Systems, devices, and methods for side lobe control in holograms

ABSTRACT

Systems, devices, and methods for side lobe control in holograms are described. The magnitude of the side lobes of a hologram depends on the distribution of refractive index modulation (Δn), therefore control of side lobe magnitude may be achieved by controlling the distribution of Δn. The distribution of Δn may be controlled by replicating a hologram from a master with two reference beams, where the wavelength and angle of each reference beam, the playback angle of the master hologram, and the thickness of the master hologram, the copy holographic recording medium (HRM), and the recording substrate are carefully chosen to achieve a pattern of meta-interference within the HRM that matches the desired distribution of Δn.

TECHNICAL FIELD

The present systems, devices, and methods generally relate to hologramsand particularly relate to controlling the side lobes in holograms.

BACKGROUND Description of the Related Art

Holograms

A hologram is a recording of a light field, with a typical light fieldcomprising a pattern of optical fringes generated by interferencebetween two beams of laser light. The hologram is made up of physicalfringes, where physical fringes comprise variations in the refractiveindex or absorbance of the holographic recording medium.

During hologram playback, at least a portion of the light field used torecord a hologram may be recreated by illuminating the hologram withlaser light. If the laser light comprises the same wavelength and angleas the first beam of laser light used to record the hologram, and thefringes have not been altered after recording, the holographic mediumwill diffract laser light with the same angle and pattern as the secondbeam of laser light used to record the hologram. The intensity of thediffracted light is determined by the efficiency of the hologram, wherethe efficiency of the hologram is the fraction of the light of the firstbeam of laser light that is diffracted in the direction of the secondbeam of laser light; hologram efficiency may be in a range from 0-100%.The efficiency of a hologram depends on both the angle and thewavelength of light used to illuminate the holographic medium. Multipleholograms may be recorded in a single holographic recording medium, themultiple holograms comprising a multiplexed hologram.

Hologram Recording

A pattern of optical fringes may be generated by the interference of twobeams of laser light; the two beams of laser light may be created bysplitting a single beam of laser light. The two beams of laser light aretypically referred to as the object beam and the reference beam.Hologram recording is typically designed such that, during playback, therecorded hologram is illuminated with laser light recreating thereference beam and the object beam is then replicated by the hologram.

Holograms are recorded in a holographic recording medium which may be asilver halide photographic emulsion, dichromated gelatin, photopolymer,or other physical media. Silver halide emulsions record a hologram as apattern of absorbance and reflectance of light. Dichromated gelatin andphotopolymer both record a hologram as a pattern of varying refractiveindex. Recording a hologram as a pattern of refractive index isadvantageous since all of the illuminating laser light may theoreticallyleave the hologram; no light is necessarily absorbed by the hologram.

Wearable Heads-Up Displays

A head-mounted display is an electronic device that is worn on a user'shead and, when so worn, secures at least one electronic display within aviewable field of at least one of the user's eyes, regardless of theposition or orientation of the user's head. A wearable heads-up displayis a head-mounted display that enables the user to see displayed contentbut also does not prevent the user from being able to see their externalenvironment. The “display” component of a wearable heads-up display iseither transparent or at a periphery of the user's field of view so thatit does not completely block the user from being able to see theirexternal environment. Examples of wearable heads-up displays include:the Google Glass®, the Optinvent Ora®, the Epson Moverio®, and the SonyGlasstron®, just to name a few.

The optical performance of a wearable heads-up display is an importantfactor in its design. When it comes to face-worn devices, however, usersalso care a lot about aesthetics. This is clearly highlighted by theimmensity of the eyeglass (including sunglass) frame industry.Independent of their performance limitations, many of the aforementionedexamples of wearable heads-up displays have struggled to find tractionin consumer markets because, at least in part, they lack fashion appeal.Most wearable heads-up displays presented to date employ large displaycomponents and, as a result, most wearable heads-up displays presentedto date are considerably bulkier and less stylish than conventionaleyeglass frames.

A challenge in the design of wearable heads-up displays is to minimizethe bulk of the face-worn apparatus will still providing displayedcontent with sufficient visual quality. There is a need in the art forwearable heads-up displays of more aesthetically-appealing design thatare capable of providing high-quality images to the user withoutlimiting the user's ability to see their external environment.

BRIEF SUMMARY

A method of producing a hologram with controlled side lobes may besummarized as including: providing a recording substrate comprising afirst surface and a second surface opposite the first surface; mountinga master hologram on the first surface of the recording substrate;mounting a holographic recording material (“HRM”) on the second surfaceof the recording substrate; replicating the master hologram within theHRM with at least two reference beams to produce a hologram withcontrolled side lobes, wherein the hologram with controlled side lobescomprises a first surface and a second surface opposite the firstsurface; and dismounting the hologram with controlled side lobes fromthe recording substrate.

The method may further include replicating the master hologram withinthe HRM with at least two reference beams to produce a hologram withcontrolled side lobes includes replicating the master hologram withinthe HRM with at least two reference beams to produce a hologram whereinthe intensity of each of the side lobes is less than one percent of theintensity of the primary hologram peak. The method may further includereplicating the master hologram within the HRM with at least tworeference beams to produce a hologram with controlled side lobesincludes replicating the master hologram within the HRM with at leasttwo reference beams to produce a hologram wherein the intensity of atleast one of the side lobes is greater than the intensity of the primaryhologram peak. The method may further include The method of claim 1,further comprising bleaching the hologram with controlled side lobes.The method may further include recording a master hologram. The methodmay further include replicating the master hologram within the HRM withat least two reference beams to produce a hologram with controlled sidelobes includes replicating the master hologram with at least tworeference beams wherein each reference beam is of a different angle thaneach other reference beam. The method may further include replicatingthe master hologram within the HRM with at least two reference beams toproduce a hologram with controlled side lobes includes replicating themaster hologram with at least two reference beams wherein each referencebeam is of a different wavelength than each other reference beam. Themethod may further include replicating the master hologram within theHRM with at least two reference beams to produce a hologram withcontrolled side lobes includes replicating a wavelength-multiplexedmaster hologram with at least two reference beams to produce awavelength-multiplexed hologram with controlled side lobes.

The wavelength multiplexed hologram with controlled side lobes maycomprise a blue hologram, a red hologram, and a green hologram, andreplicating a wavelength-multiplexed master hologram with at least tworeference beams to produce a wavelength-multiplexed hologram withcontrolled side lobes may include replicating a wavelength-multiplexedmaster hologram comprising a blue master hologram, a red masterhologram, and a green master hologram.

Replicating a wavelength-multiplexed master hologram comprising a bluemaster hologram, a red master hologram, and a green master hologram mayinclude replicating a wavelength-multiplexed master hologram comprisinga blue master hologram, a red master hologram, and a green masterhologram wherein the bandwidth of the red master hologram is greaterthan the bandwidth of the green master hologram, and the bandwidth ofthe green master hologram may be greater than the bandwidth of the bluemaster hologram. Replicating a wavelength-multiplexed master hologrammay include replicating a wavelength-multiplexed master hologram with atleast two blue beams of laser light, at least two green beams of laserlight, and at least two red beams of laser light.

Replicating a wavelength-multiplexed master hologram with at least twoblue beams of laser light, at least two green beams of laser light, andat least two red beams of laser light may include: replicating thewavelength-multiplexed master hologram with two blue beams of laserlight wherein the two blue beams of laser light differ in wavelength bya first Δλ; replicating the wavelength-multiplexed master hologram withtwo green beams of laser light wherein the two green beams of laserlight differ in wavelength by a second Δλ; and replicating thewavelength-multiplexed master hologram with two red beams of laser lightwherein the two red beams of laser light differ in wavelength by a thirdΔλ; wherein the first ΔA may be less than the second Δλ and the secondΔλ may be less than the third Δλ.

Replicating the master hologram within the HRM with at least tworeference beams to produce a hologram with controlled side lobes mayinclude replicating the master hologram with at least two referencebeams to record an initial set of fringes and at least one additionalset of fringes within the HRM, wherein the initial set of fringes maypossess a phase within the HRM, each additional set of fringes maypossess a net phase shift relative to the initial set of fringes withinthe HRM, and wherein the initial set of fringes and each additional setof fringes may meta-interfere.

Replicating the master hologram with at least two reference beams torecord an initial set of fringes and at least one additional set offringes within the HRM may include replicating the master hologram withat least two reference beams to record an initial set of fringes and atleast one additional set of fringes within the HRM wherein: the initialset of fringes and each additional set of fringes may meta-interferemost destructively at a depth within the hologram corresponding to atleast one of: the first surface and the second surface; and the initialset of fringes and each additional set of fringes may meta-interferemost constructively at a depth between the first surface and the secondsurface.

Replicating the master hologram with at least two reference beams torecord an initial set of fringes and at least one additional set offringes within the HRM may include replicating the master hologram withat least two reference beams to record an initial set of fringes and atleast one additional set of fringes within the HRM wherein: the initialset of fringes and each additional set of fringes may meta-interferemost constructively at a depth within the hologram corresponding to atleast one of: the first surface and the second surface; and the initialset of fringes and each additional set of fringes may meta-interferemost destructively at a depth between the first surface and the secondsurface.

The master hologram may possess a Bragg peak wavelength, each referencebeam may possess a reference beam wavelength, and wherein replicatingthe master hologram within the HRM with at least two reference beams toproduce a hologram with controlled side lobes may include replicatingthe master hologram within the HRM with at least two reference beams toproduce a hologram with controlled side lobes wherein the differencebetween the Bragg peak wavelength of the master hologram and referencebeam wavelength of each reference beam may be less than 2 nanometers.

Replicating the master hologram within the HRM with at least tworeference beams to produce a hologram with controlled side lobes mayinclude replicating the master hologram within the HRM with at least tworeference beams to produce a hologram with controlled side lobes whereinat least one of the reference beams may comprise a plane wave.Replicating the master hologram within the HRM with at least tworeference beams to produce a hologram with controlled side lobes mayinclude replicating the master hologram within the HRM with at least tworeference beams to produce a hologram with controlled side lobes whereinat least one of the reference beams comprises a spherical wave.

A hologram with controlled side lobes may be summarized as including: afirst surface; a second surface opposite the first surface; an initialset of fringes within the volume of the hologram, the initial set offringes comprising an initial fringe phase, an initial fringe spacingand an initial fringe slant angle; and at least one additional set offringes within the volume of the hologram, wherein each additional setof fringes comprises a respective net phase shift relative to the phaseof the initial set of fringes, an additional fringe spacing, and anadditional fringe slant angle wherein each additional fringe spacing isequal to the initial fringe spacing, each additional fringe slant angleis not equal to the initial fringe slant angle or any other additionalfringe slant angle, the initial set of fringes and all additional setsof fringes meta-interfere, and the magnitude of Δn within the hologramvaries between the first surface and the second surface.

The intensity of each of the side lobes may be less than one percent ofthe intensity of the primary hologram peak. The intensity of at leastone of the side lobes may greater than the intensity of the primaryhologram peak. The hologram may further include: the initial set offringes and each additional set of fringes may meta-interfere mostconstructively at a depth through the hologram between the first surfaceand the second surface; the initial set of fringes and each additionalset of fringes may meta-interfere at least partially destructively atthe first surface; the initial set of fringes and each additional set offringes may meta-interfere at least partially destructively at thesecond surface; the magnitude of Δn at the first surface may be equal toor less than 50% of the greatest magnitude of Δn within the hologram;and the magnitude of Δn at the second surface may be equal to or lessthan 50% of the greatest magnitude of Δn within the hologram. Themagnitude of Δn may increase continuously from the first surface to themaximum value of Δn within the hologram and the magnitude of Δn mayincrease continuously from the second surface to the maximum value of Δnwithin the hologram. The hologram may include: the initial set offringes and each additional set of fringes may meta-interfere mostdestructively at a depth through the hologram between the first surfaceand the second surface; the initial set of fringes and each additionalset of fringes may meta-interfere at least partially constructively atthe first surface; the initial set of fringes and each additional set offringes may meta-interfere at least partially constructively at thesecond surface; at least one of: the first surface and the secondsurface may possess the greatest magnitude of Δn; the minimum magnitudeof Δn within the volume of the hologram may be no greater than 50% ofthe greatest magnitude of Δn within the hologram; and the magnitude ofΔn may decreases continuously from the first surface to the minimumvalue of Δn within the hologram and the magnitude of Δn decreasescontinuously from the second surface to the minimum value of Δn withinthe hologram.

The hologram may comprise a wavelength-multiplexed hologram. Thewavelength-multiplexed hologram may comprises a blue hologram, a greenhologram, a red hologram, and an infrared hologram. The hologram mayfurther include: the intensity of the side lobes of the blue hologramrelative to the intensity of primary peak of the blue hologram may beequal to the intensity of the side lobes of the green hologram relativeto the intensity of primary peak of the green hologram; the intensity ofthe side lobes of the green hologram relative to the intensity ofprimary peak of the green hologram may be equal to the intensity of theside lobes of the red hologram relative to the intensity of primary peakof the red hologram; and the intensity of the side lobes of the redhologram relative to the intensity of primary peak of the red hologrammay be equal to the intensity of the side lobes of the infrared hologramrelative to the intensity of primary peak of the infrared hologram.

A hologram with controlled side lobes recording system may be summarizedas including: a recording substrate comprising a master-side surface andcopy-side surface; a copy holographic recording medium (“HRM”)comprising a first copy HRM surface and a second copy HRM surface,wherein the first copy surface is physically coupled to the copyHRM-side surface of the recording substrate; a master hologramcomprising master hologram fringes wherein the master hologram isphysically coupled to the master-side surface; a laser light source; afirst reference beam produced by the laser light source, wherein thefirst reference beam passes through the copy HRM, passes through therecording substrate, and impinges on the master hologram; a secondreference beam produced by the laser light source, wherein the secondreference beam passes through the copy HRM, passes through the recordingsubstrate, and impinges on the master hologram; a first diffractedobject beam, wherein the first diffracted object beam passes through therecording substrate and passes through the copy HRM; and a seconddiffracted object beam, wherein the second diffracted object beam passesthrough the recording substrate and passes through the copy HRM.

The second reference beam may be of a different wavelength than thefirst reference beam. The second reference beam may be of a differentangle than the first reference beam. The first reference beam and thefirst diffracted object beam may interfere to produce an initial set offringes, the second reference beam and the second diffracted object beammay interfere to form an additional set of fringes, and the initial setof fringes and the additional set of fringes may meta-interfere. Theinitial set of fringes and each additional set of fringes maymeta-interfere most destructively at a depth within the hologramcorresponding to at least one of: the first copy HRM surface and thesecond copy HRM surface and the initial set of fringes and eachadditional set of fringes may meta-interfere most constructively at adepth equidistant between the first copy HRM surface and the second copyHRM surface. The initial set of fringes and each additional set offringes may meta-interfere most constructively at a depth within thehologram corresponding to at least one of: the first copy HRM surfaceand the second copy HRM surface and the initial set of fringes and eachadditional set of fringes may meta-interfere most destructively at adepth equidistant between the first copy HRM surface and the second copyHRM surface.

The master hologram may comprise a wavelength-multiplexed masterhologram, the wavelength-multiplexed master hologram comprising: a redhologram; a green hologram; and a blue hologram; and wherein thehologram with controlled side lobes recording system may furthercomprise: at least two blue reference beams; at least two greenreference beams; and at least two red reference beams.

An eyeglass lens for use in a wearable heads-up display may besummarized as including: a hologram with controlled side lobescomprising: a first surface; a second surface opposite the firstsurface; an initial set of fringes within the volume of the hologramcomprising an initial fringe spacing and an initial slant angle; and atleast one additional set of fringes within the volume of the hologram,wherein each additional set of fringes comprises a respective net phaseshift relative to the phase of the initial set of fringes, an additionalfringe spacing, and an additional fringe slant angle wherein eachadditional fringe spacing is equal to the initial fringe spacing, eachadditional fringe slant angle is not equal to the initial fringe slantangle or any other additional fringe slant angle, the initial set offringes and all additional sets of fringes meta-interfere, and themagnitude of Δn within the hologram varies between the first surface andthe second surface; and at least one lens portion, wherein each lensportion is physically coupled to the hologram with controlled sidelobes.

The intensity of each of the side lobes of the hologram may be less thanone percent of the intensity of the primary hologram peak. The intensityof at least one of the side lobes of the hologram may be greater thanthe intensity of the primary hologram peak. The initial set of fringesand each additional set of fringes may meta-interfere mostconstructively at a depth through the hologram between the first surfaceand the second surface; the initial set of fringes and each additionalset of fringes may meta-interfere at least partially destructively atthe first surface; the initial set of fringes and each additional set offringes may meta-interfere at least partially destructively at thesecond surface; the magnitude of Δn at the first surface may be equal toor less than 50% of the greatest magnitude of Δn within the hologram;and the magnitude of Δn at the second surface may be equal to or lessthan 50% of the greatest magnitude of Δn within the hologram. Theinitial set of fringes and each additional set of fringes maymeta-interfere most destructively at a depth through the hologrambetween the first surface and the second surface; the initial set offringes and each additional set of fringes may meta-interfere at leastpartially constructively at the first surface; the initial set offringes and each additional set of fringes may meta-interfere at leastpartially constructively at the second surface; at least one of: thefirst surface and the second surface may possess the greatest magnitudeof Δn; the minimum magnitude of Δn within the volume of the hologram maybe no greater than 50% of the greatest magnitude of Δn within thehologram; and the magnitude of Δn may decrease continuously from thefirst surface to the minimum value of Δn within the hologram and themagnitude of Δn decreases continuously from the second surface to theminimum value of Δn within the hologram. The hologram may include awavelength-multiplexed hologram, the wavelength-multiplexed hologramcomprising a blue hologram, a green hologram, a red hologram, and aninfrared hologram.

A wearable heads-up display may be summarized as including: a supportstructure; a projector; and a transparent combiner positioned andoriented to appear in a field of view of an eye of a user when thesupport structure is worn on a head of the user, the transparentcombiner comprising: a hologram with controlled side lobes comprising: afirst surface; a second surface opposite the first surface; an initialset of fringes within the volume of the hologram comprising an initialfringe spacing and an initial slant angle; and at least one additionalset of fringes within the volume of the hologram, wherein eachadditional set of fringes comprises a given additional fringe spacingand a given additional slant angle wherein each additional fringespacing is equal to the initial fringe spacing, each additional slantangle is not equal to the initial slant angle or any other additionalslant angle, the initial set of fringes and all additional sets offringes meta-interfere, and the magnitude of Δn within the hologramvaries between the first surface and the second surface; and at leastone lens portion, wherein each lens portion is physically coupled to thehologram with controlled side lobes.

The intensity of each of the side lobes of the hologram may be less thanone percent of the intensity of the primary hologram peak. The intensityof at least one of the side lobes of the hologram may be greater thanthe intensity of the primary hologram peak. The initial set of fringesand each additional set of fringes may meta-interfere mostconstructively at a depth through the hologram between the first surfaceand the second surface; the initial set of fringes and each additionalset of fringes may meta-interfere at least partially destructively atthe first surface; the initial set of fringes and each additional set offringes may meta-interfere at least partially destructively at thesecond surface; the magnitude of Δn at the first surface may be equal toor less than 50% of the greatest magnitude of Δn within the hologram;and the magnitude of Δn at the second surface may be equal to or lessthan 50% of the greatest magnitude of Δn within the hologram. Theinitial set of fringes and each additional set of fringes maymeta-interfere most destructively at a depth through the hologrambetween the first surface and the second surface; the initial set offringes and each additional set of fringes may meta-interfere at leastpartially constructively at the first surface; the initial set offringes and each additional set of fringes may meta-interfere at leastpartially constructively at the second surface; at least one of: thefirst surface and the second surface may possess the greatest magnitudeof Δn; the minimum magnitude of Δn within the volume of the hologram maybe no greater than 50% of the greatest magnitude of Δn within thehologram; and the magnitude of Δn may decrease continuously from thefirst surface to the minimum value of Δn within the hologram and themagnitude of Δn may decrease continuously from the second surface to theminimum value of Δn within the hologram. The hologram may comprise awavelength-multiplexed hologram, the wavelength-multiplexed hologramcomprising a blue hologram, a green hologram, a red hologram, and aninfrared hologram.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the drawings, identical reference numbers identify similar elementsor acts. The sizes and relative positions of elements in the drawingsare not necessarily drawn to scale. For example, the shapes of variouselements and angles are not necessarily drawn to scale, and some ofthese elements are arbitrarily enlarged and positioned to improvedrawing legibility. Further, the particular shapes of the elements asdrawn are not necessarily intended to convey any information regardingthe actual shape of the particular elements, and have been solelyselected for ease of recognition in the drawings.

FIG. 1 is a flow-diagram showing a method of producing a hologram withcontrolled side lobes in accordance with the present systems, devices,and methods.

FIG. 2 is a cross-sectional view of hologram with controlled side lobesin accordance with the present systems, devices, and methods.

FIG. 3A is a cross-sectional view of hologram with unmatched fringespacing in accordance with the present systems, devices, and methods.

FIG. 3B is a cross-sectional view of hologram with unmatched phase inaccordance with the present systems, devices, and methods.

FIG. 4 is a cross-sectional view of hologram with controlled side lobesrecording system in accordance with the present systems, devices, andmethods.

FIG. 5 is a cross-sectional view of an exemplary eyeglass lens with anembedded hologram with controlled side lobes suitable for use as atransparent combiner in a WHUD in accordance with the present systems,devices, and methods.

FIG. 6 is a partial-cutaway perspective view of a WHUD that includes aneyeglass lens with an embedded hologram with controlled side lobes inaccordance with the present systems, devices, and methods.

FIG. 7 is a cross-sectional view of hologram with controlled side lobesin accordance with the present systems, devices, and methods.

FIG. 8 is a cross-sectional view of an exemplary eyeglass lens withcomprising a light guide and a hologram with controlled side lobes inaccordance with the present systems, devices, and methods.

DETAILED DESCRIPTION

In the following description, certain specific details are set forth inorder to provide a thorough understanding of various disclosedembodiments. However, one skilled in the relevant art will recognizethat embodiments may be practiced without one or more of these specificdetails, or with other methods, components, materials, etc. In otherinstances, well-known structures associated with portable electronicdevices and head-worn devices, have not been shown or described indetail to avoid unnecessarily obscuring descriptions of the embodiments.

Unless the context requires otherwise, throughout the specification andclaims which follow, the word “comprise” and variations thereof, suchas, “comprises” and “comprising” are to be construed in an open,inclusive sense, that is as “including, but not limited to.”

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structures, orcharacteristics may be combined in any suitable manner in one or moreembodiments.

As used in this specification and the appended claims, the singularforms “a,” “an,” and “the” include plural referents unless the contentclearly dictates otherwise. It should also be noted that the term “or”is generally employed in its broadest sense, that is as meaning “and/or”unless the content clearly dictates otherwise.

The headings and Abstract of the Disclosure provided herein are forconvenience only and do not interpret the scope or meaning of theembodiments.

The various embodiments described herein provide systems, devices, andmethods for side lobe control in holograms and are particularlywell-suited for use in wearable heads-up displays (WHUDs).

A hologram is a repeating pattern of physical fringes that, whenilluminated with coherent light with the same wavelength and angle asone of the lasers used to record the fringes, diffracts at least aportion of the incident light at an angle equal to the angle of theother laser used to record the physical fringes; the wavelength of thelight remains unchanged. Physical fringes may comprise local maxima (orminima) of refractive index within a recorded hologram. Physical fringesare the physical structures that comprise the recorded hologram.

A holographic optical element (HOE) comprises a hologram. A HOE maycomprise one or more cover sheets. A cover sheet comprises a transparentmaterial physically coupled to a surface of the hologram, cover sheetsare advantageous as they may improve the strength, durability, scratchresistance, or ease of adhesion of the HOE.

A hologram may be recorded within a holographic recording medium (HRM).A HRM comprises photosensitive material which undergoes a chemical orphysical change upon exposure to light. When a HRM is exposed to apattern of optical fringes, the photosensitive material records thepattern of optical fringes as a pattern of physical fringes. HRMs aretypically physically coupled to at least one transparent supportcovering at least one surface of the HRM. The transparent supportmaintains the shape of the HRM before, during, and after hologramrecording; the transparent support may also protect the HRM from damage.Non-exclusive examples of materials which may comprise a transparentsupport include glass, polycarbonate, polystyrene, acrylic, or otheroptical plastic materials.

HRMs are typically flat, planar materials with a thickness less than 0.1mm; however, HRMs may have a thickness of up to 1 mm and may be curved.A curved surface may be a spherically curved surface; a sphericallycurved surface is curved around a center of curvature. A curved surfacemay be a cylindrically curved surface; a cylindrically curved surface iscurved around an axis of curvature. The center or axis of curvature, asappropriate, of the HRM may be located at a distance of between 1 and 10centimeters, between 10 and 50 cm, or between 50 and 100 cm from thesurface of the HRM.

A side lobe in a hologram is a local maximum adjacent to the primarypeak in a plot of hologram efficiency versus either wavelength or angleof incidence. Side lobes may arise from the sharp difference inrefractive index modulation (Δn) between where the hologram is recordedwithin the HOE and where the hologram is not recorded within thetransparent support. Δn (i.e., refractive index modulation) is thedifference between the highest and lowest refractive indices in arecorded hologram.

In a typical hologram, Δn as a function of depth through the hologramcan be described by a square-wave function. Within a hologram, depth isthe distance from a surface of the hologram to a point within thehologram measured in the z direction, where the z direction is normal tothe surface of the plane, cylinder, or sphere of the hologram film (forplanar, cylindrical, and spherical holograms, respectively).

Since the efficiency of the hologram with respect to either wavelengthor angle is the Fourier transform of Δn as a function of depth, theefficiency response of a typical hologram is the Fourier transform of asquare wave function. A sinc function (an abbreviation of “sine cardinalfunction”) is a mathematical function that describes the Fouriertransform of a square wave function; a sinc squared function is thesquare of a sinc function. A sinc squared function possesses a primarypeak and multiple side lobes, therefore a hologram with a Δn profileequivalent to a square-wave function also has side lobes.

The presence of side lobes in a hologram may create a number ofpotential problems. A hologram recorded at a particular wavelength willbe responsive to wavelengths outside the desired primary playbackwavelength and therefore produce playback light when illuminated withlight with a wavelength higher or lower than the wavelength used torecord the hologram. Playback is the process of illuminating a hologramwith light that replicates the reference beam in order to replicate theobject beam. The reference beam is one of the laser beams used to recordthe hologram, the object beam is another laser used to record thehologram.

For example, a hologram recorded with green laser light could produceplayback light when illuminated with blue laser light if the blue laserlight is of a wavelength corresponding to one of the side lobes of thehologram recorded with green laser light; the same green hologram mayalso produce playback light when illuminating the hologram with redlaser light matching another side lobe of the green hologram. Theplayback light produced by the side lobes will have a different playbackangle than the playback light produced by the primary peak.

The creation of additional playback beams at multiple angles due to sidelobes is problematic when a hologram is used in a holographic display,including a holographic WHUD. If the additional playback beams are ableto enter the eye of the user, the additional playback beams createsecondary visible images displaced in space from the primary image beingproduced by the display. These additional images are typically lower inintensity than the main image and are referred to as “ghost images”.Ghost images may reduce the resolution of the display by blurring anyimages produced by the display, and ghost images may also occlude theprimary images of the display if the ghost image produced by one portionof the primary image overlaps another portion of the primary image.

Ghost image formation may be reduced or eliminated by reducing oreliminating, respectively, the presence of side lobes in the hologram.Softening the edges of the Δn profile as a function of depth reduces thestrength of the side lobes. Apodizing the Δn profile as a function ofdepth significantly reduces or eliminates the presence of side lobes. Anapodized hologram is a hologram with a minimum value of Δn at both themaximum and minimum depth of the hologram, a maximum value of Δn at someintermediate depth of the hologram, and no observable local maxima orminima of Δn through the depth of the hologram. Alternatively, if sidelobes are desired, the side lobes could be accentuated by anti-apodizingthe Δn profile as a function of depth.

A hologram with controlled side lobes comprises a hologram with sidelobes that differ from the side lobes present in a hologram recordedwith a single reference beam; in other words a hologram with controlledside lobes comprises a hologram with side lobes that are either greateror lesser in magnitude than the side lobes described by a sinc function.

Described herein is a method of producing holograms with controlled sidelobes, the resulting holograms, and components, systems, and devicescomprising holograms with controlled side lobes.

FIG. 1 is a flow-diagram showing a method 100 of producing a hologramwith controlled side lobes 100 in accordance with the present systems,devices, and methods. Method 100 includes five acts 101, 102, 103, 104,and 105 though those of skill in the art will appreciate that inalternative embodiments certain acts may be omitted and/or additionalacts may be added. Those of skill in the art will also appreciate thatthe illustrated order of the acts is shown for exemplary purposes onlyand may change in alternative embodiments.

At 101, a recording substrate is provided. The recording substratecomprises a first surface and a second surface. A master hologram is arecorded hologram that may be used repeatedly to replicate a hologram ina second (or copy) holographic recording medium (HRM). Replication isthe process of recording a copy hologram using a master and includescontact and non-contact copying, with contact copying being moretypically used for mass production. In contact copying, the master isaffixed to a first surface of a recording substrate.

A recording substrate is an inflexible transparent substrate thatdefines the shape of a hologram during recording. Typical recordingsubstrates are flat and planar, however recording substrates may be atleast partially spherically curved and/or at least partiallycylindrically curved; typical recording substrate materials includeglass and polycarbonate. A HRM is affixed to a second surface of therecording substrate, where the second surface is opposite the firstsurface. A reference beam is passed through the HRM, the substrate, andthe master. The master diffracts at least a portion of the referencebeam to produce a diffracted object beam. The diffracted object beam andthe reference beam interfere within the HRM, recording a hologram withinthe HRM that is substantively similar to the hologram recorded withinthe master.

Contact copying is advantageous because the minimal distance between themaster and the copy ensures that the path length difference between thereference beam and diffracted object beam is very small, allowing theuse of less expensive laser light sources with shorter coherencelengths. Since contact copying includes physically coupling the masterand copy hologram to the same substrate, motion of the copy hologramrelative to the master hologram during recording is essentiallyeliminated and stringent vibration control is no longer needed.

At 102, a master hologram is mounted on the first surface of therecording substrate. Mounting the master hologram on the recordingsubstrate includes physically coupling the master hologram to the firstsurface of the recording substrate.

At 103, a HRM is mounted on the recording substrate. Mounting the HRM onthe recording substrate includes physically coupling the HRM to thesecond surface of the recording substrate, wherein the second surface ofthe recording substrate is opposite the first surface of the recordingsubstrate.

At 104, the master hologram is replicated within the HRM with at leasttwo reference beams to produce a hologram with controlled side lobes.The at least two reference beams may each be of a different wavelengththan each other reference beam. The at least two reference beams mayeach be of a different angle than each other reference beam.

Replicating the master hologram within the HRM with at least tworeference beams to produce a hologram with controlled side lobes mayinclude replicating the master hologram within the HRM with at least tworeference beams to produce a hologram wherein the intensity of the sidelobes is less than 25%, less than 10%, or less than one percent of theintensity of the primary hologram peak. Side lobes with minimalintensity relative to the primary hologram peak may be produced byapodizing the distribution of Δn as a function of depth within thehologram. Replicating the master hologram within the HRM with at leasttwo reference beams to produce a hologram with controlled side lobes mayinclude replicating the master hologram within the HRM with at least tworeference beams to produce a hologram wherein the intensity of at leastone of the side lobes is at least 25% of, at least 50% of, or greaterthan the intensity of the primary hologram peak. Side lobes with maximalintensity relative to the primary hologram peak may be produced byanti-apodizing the distribution of Δn as a function of depth within thehologram.

Replicating the master hologram with at least two reference beams willproduce at least two diffracted object beams; each of the at least twodiffracted object beams will interfere with each of the at least tworeference beams to produce at least two sets of optical fringes (atleast a portion of each set of optical fringes is located within aninternal volume of the HRM). The light diffracted by the master hologramfollows the diffraction grating equation:

$\frac{\lambda}{n\; \Lambda} = {{\sin \; \theta_{1}} - {\sin \; \theta_{2}}}$

where λ is the wavelength of the laser light, Λ is the lateral gratingspacing (of the optical fringes), θ₁ is the angle of incidence (relativeto the normal), θ₂ is the angle of diffraction (relative to the normal),and n is an integer. The lateral spacing of the fringes produced byinterference between incident light and any light produced by the masterhologram will be the same; any changes in incident wavelength or anglewill affect the angle of the diffracted light (and therefore the angleof the resulting fringes) but not the spacing of the resulting fringes.The fringe spacing is always the same when replicating a single masterwith two laser beams, thus the at least two sets of optical fringes willboth possess the same fringe spacing as the master hologram. The atleast two sets of optical fringes may be recorded within the HRM to format least two sets of physical fringes.

In other words, replicating the master hologram with at least tworeference beams includes illuminating the HRM and the master hologramwith at least two reference beams; during replication the masterhologram and the HRM are separated from one another by the recordingsubstrate. Replicating the master hologram within the HRM includespassing each reference beam through the HRM, the recording substrate,and the master hologram. Replicating a transmission hologram includespassing each reference beam through the master hologram prior to passingeach reference beam through the HRM. Replicating a reflection hologramincludes passing each reference beam through the HRM prior to passingeach reference beam through the master hologram.

Replication may include recording a pattern of fringes within HRM thatis substantively similar to the pattern of fringes within the masterhologram. During replication, each reference beam possesses a phasewithin the HRM and each object beam possesses a phase within the HRM.Both the reference beam and the object beam must pass through therecording substrate, but the path length through the recording substrateof the reference beam is not necessarily equal to the path lengththrough the recording substrate of the object beam. The difference inpath length between the object beam and the reference beam causes aphase shift between the object beam and the reference beam within theHRM. The phase of the optical fringes produced by interference betweenthe object beam and the reference beam within the HRM depends on thephase shift between the object beam and the reference beam.

Throughout this specification and the appended claims, the term“meta-interference” refers to interference between sets of fringes; eachset of fringes may be the product of interference between each referencebeam and the respective object beam diffracted from each reference beam.Replicating the master hologram within the HRM with at least tworeference beams produces at least two sets of optical fringes thatundergo meta-interference. The meta-interference of the at least twosets of optical fringes increases Δn in regions of constructivemeta-interference and decreases Δn in regions of destructivemeta-interference. The magnitude of the increase or decrease in Δndepends on the magnitude of the constructive or destructivemeta-interference, respectively. The position of the increased ordecreased Δn within the HRM depends on the net phase shift of each setof fringes, where the net phase shift of a set of optical fringes is therelative difference in phase between that set of optical fringes andanother set of optical fringes within the HRM.

Control over the side lobes of a hologram requires control over thepositions of high and low Δn within the HRM. Control over the positionsof high and low Δn within the HRM may be achieved by controlling theprecise angle and wavelength of each reference beam employed duringreplication. The angle and wavelength of each reference beam determinesthe phase shift of each object beam, and therefore the phase of each setof optical fringes, the net phase shift between each set of opticalfringes, the meta-interference between sets of optical fringes, andthereby the positions of high and low Δn within the HRM.

Consider FIG. 2, which shows a cross-sectional view of hologram withcontrolled side lobes 200 in accordance with the present systems,devices, and methods. Hologram with controlled side lobes 200 may beproduced by method 100. Hologram with controlled side lobes 200comprises first set of fringes 210 and second set of fringes 220. Firstset of fringes 210 and second set of fringes 220 may be formed byreplicating a master hologram with two reference beams. First set offringes 210 and second set of fringes 220 have the same spacing butdifferent angles, which causes first set of fringes 210 and second setof fringes 220 to interfere with each other. At the top and bottomsurface of hologram with controlled side lobes 200 first set of fringes210 and second set of fringes 220 interfere destructively, reducing Δnto a minimum. At the middle depth of hologram with controlled side lobes200 first set of fringes 210 and second set of fringes 220 interfereconstructively, increasing Δn to a maximum. Δn increases smoothly fromeither surface of the hologram towards the maximum. Hologram withcontrolled side lobes 200 is therefore apodized and will have minimal,if any, side lobes. In order to achieve this smooth interference betweensets of fringes with a maximum Δn at a desired depth, the sets offringes must have precisely matched spacing and phase.

First set of fringes 210 may comprise an initial set of fringes. Secondset of fringes 220 may comprise an additional set of fringes. A personof skill in the art will appreciate that for the sake of clarity onlytwo sets of fringes are depicted in Figure two, however hologram withcontrolled side lobes 200 may comprise n sets of fringes (where n isequal to or greater than 2) with one initial set of fringes and n−1additional sets of fringes, the various sets of fringes having differentangles and, or different phase shifts from those of the other sets offringes.

In some implementations, hologram 200 may be carried on or by anotherstructure, and such other structure may, for example, provide at leastsome additional optical function. For instance, one or more hologramsmay be carried on or by a waveguide or lightguide structure and mayserve as, for example, an in-coupler, out-coupler, or exit pupilexpander for such waveguide or lightguide structure. Thus, for thepurposes of the present systems, device, and methods, including theappended claims, the term “hologram” may include a HRM layer and acombination of optional additional layers or structures such asprotective material, waveguide/lightguide structures, substrates, etc.depending on the specific implementation. Likewise, when the term“hologram with controlled side lobes” is used, said hologram withcontrolled side lobes may be carried on or by other structures orlayers, or may itself carry other structures or layers, depending on thespecific implementation.

Returning to FIG. 1, replicating the master hologram within the HRM withat least two reference beams to produce a hologram with controlled sidelobes may include replicating a wavelength-multiplexed master hologramwith at least two reference beams to produce a wavelength-multiplexedhologram with controlled side lobes. A wavelength-multiplexed hologramis a hologram comprising multiple wavelength-specific holograms. Eachwavelength-specific hologram comprising a wavelength-multiplexedhologram diffracts laser light of a specific wavelength; awavelength-specific hologram cannot diffract light of a wavelengthoutside of the spectral bandwidth of the wavelength-specific hologram.Wavelength-multiplexed holograms are advantageous since awavelength-multiplexed hologram may be employed as a holographiccombiner in a WHUD with a full-color display; single-wavelengthholograms may be employed in monochromatic displays.

A wavelength-multiplexed master hologram may be replicated to produce awavelength-multiplexed hologram with controlled side lobes. Awavelength-multiplexed master hologram may comprise a blue masterhologram, a green master hologram, and a red master hologram. Awavelength-multiplexed hologram with controlled side lobes may comprisea blue hologram with controlled side lobes, a green hologram withcontrolled side lobes, and a red hologram with controlled side lobes. Awavelength-multiplexed hologram with controlled sidelobes may bereplicated from a wavelength-multiplexed master hologram with at leasttwo blue beams of laser light, at least two green beams of laser light,and at least two red beams of laser light. Each beam of laser light usedto replicate a wavelength-multiplexed hologram with controlled sidelobesfrom a wavelength-multiplexed possesses a respective wavelength.

A blue wavelength-specific hologram with controlled sidelobes comprisinga wavelength-multiplexed hologram with controlled sidelobes may bereplicated from a wavelength-multiplexed master with two blue beams oflaser light, where the two blue beams of laser light differ inwavelength by a first Δλ. A green wavelength-specific hologram withcontrolled sidelobes comprising a wavelength-multiplexed hologram withcontrolled sidelobes may be replicated from a wavelength-multiplexedmaster with two green beams of laser light, where the two green beams oflaser light differ in wavelength by a second Δλ. A redwavelength-specific hologram with controlled sidelobes comprising awavelength-multiplexed hologram with controlled sidelobes may bereplicated from a wavelength-multiplexed master with two red beams oflaser light, where the two red beams of laser light differ in wavelengthby a third Δλ. The first Δλ may be greater than, less than, or equal tothe second Δλ. The second Δλ may be greater than, less than, or equal tothe third Δλ. A wavelength-multiplexed hologram with controlled sidelobes, where each wavelength-specific hologram has the same intensity ofside lobes relative to the intensity of the primary hologram peak, maybe replicated when the first Δλ is highest and the third Δλ is lowest.

The master hologram possesses a Bragg peak wavelength. Each referencebeam possesses a reference beam wavelength. Replicating the masterhologram within the HRM with at least two reference beams to produce ahologram with controlled side lobes may include replicating the masterhologram within the HRM with at least two reference beams to produce ahologram with controlled side lobes wherein the difference between theBragg peak wavelength of the master hologram and reference beamwavelength of each reference beam is less than 2 nanometers. Replicatingthe master hologram with a reference beam wherein the difference betweenthe Bragg peak wavelength of the master hologram and the reference beamwavelength is small is advantageous since the efficiency of the masterhologram may decrease significantly at wavelengths greater than 2nanometers from the Bragg peak wavelength of the master hologram.Significant changes in master hologram efficiency may cause significantchanges in the phase of any laser light diffracted by the masterhologram, and therefore make it difficult to control the phase of theinitial set of optical fringes and the net phase shift of the additionalsets of optical fringes within the HRM.

The bandwidth of a hologram is the range of angles and wavelengths ofincident laser light that the hologram efficiently diffracts; bandwidthincludes angular bandwidth and wavelength bandwidth. The angularbandwidth of a hologram is the range of angles of incident laser lightthat satisfies the Bragg condition for the hologram and therefore may beefficiently diffracted by the hologram. The wavelength bandwidth of ahologram is the range of wavelengths of incident laser light thatsatisfies the Bragg condition for the hologram and therefore may beefficiently diffracted by the hologram. Typically, a hologram with anarrow angular bandwidth also possesses a narrow wavelength bandwidthand a hologram with a broad angular bandwidth also possesses a broadwavelength bandwidth. Any process that increases or decreases theangular bandwidth of a hologram will typically also proportionallyincrease or decrease (respectively) the wavelength bandwidth of ahologram. A person of skill of art will appreciate that the term“bandwidth” therefore may refer either to the angular bandwidth or thewavelength bandwidth of a hologram unless otherwise specified as“angular bandwidth” or “wavelength bandwidth”. Each wavelength-specifichologram comprising a wavelength-multiplexed hologram possesses its ownbandwidth. In other words, for a wavelength-multiplexed hologramcomprising a blue hologram, a green hologram, and a red hologram, thebandwidth of the blue hologram may be greater than or less than thebandwidth of the green hologram, and the bandwidth of the green hologrammay be greater than or less than the bandwidth of the red hologram. Thephase shift introduced to the diffracted object beam by the masterhologram due to the thickness of the master hologram depends on thebandwidth of the master hologram. A hologram with broader bandwidth willhave a weaker dependence of phase shift on hologram thickness; varyingthe bandwidth of the wavelength-specific holograms allows furthercontrol of the phase shift of the respective diffracted object beams andtherefore the side lobes of the resulting holograms.

Replicating the master hologram within the HRM with at least tworeference beams to produce a hologram with controlled side lobes mayinclude replicating the master hologram with at least two referencebeams to record an initial set of fringes and at least one additionalset of fringes within the HRM. The initial set of fringes possesses aphase within the HRM. Each additional set of fringes possesses a netphase shift relative to the initial set of fringes within the HRM. Thenet phase shift between each additional set of fringes and the initialset of fringes controls the meta-interference between each additionalset of fringes and the initial set of fringes.

A person of skill in the art will appreciate that defining a particularset of fringes as being an initial set of fringes (while all other setsof fringes are additional fringes) is advantageous as such a definitionestablishes a common frame of reference for determining the phase ofeach set of fringes relative to each other set of fringes. Adetermination of the relative phase of each set of fringes may eliminatethe need to determine the absolute phase of any set of fringes.

Each set of fringes (initial or additional) will meta-interfere witheach other set of fringes within the HRM. Constructive meta-interferencebetween sets of fringes increases Δn, while destructivemeta-interference between sets of fringes decreases Δn. The locationswithin the HRM where fringes meta-interfere constructively ordestructively depends on the phase of the initial set of fringes withinthe HRM and the net phase shift of the at least one additional set offringes within the HRM. The net phase shift of each additional set offringes may be expressed in radians. The net phase shift of eachadditional set of fringes may be measured at a depth within the hologramequidistant from the first surface and the second surface of the HRM. Anet phase shift of 0 will result in maximum constructivemeta-interference at a depth within the hologram equidistant from thefirst surface and the second surface of the HRM and maximum destructivemeta-interference at the first surface and at the second surface; inother words, a net phase shift of 0 will produce an apodized hologramwith minimized side lobes. A net phase shift of π will result in maximumdestructive meta-interference at a depth within the hologram equidistantfrom the first surface and the second surface of the HRM and maximumconstructive meta-interference at the first surface and at the secondsurface; in other words, a phase shift of π will produce ananti-apodized hologram with maximized side lobes.

Factors that determine the phase of the initial set of fringes withinthe HRM include: the thickness of the recording substrate, therefractive index of the recording substrate, the thickness of the masterhologram, the bandwidth of the master hologram, the angle of thereference beam diffracted by the master hologram to produce the initialset of fringes, and the wavelength of the reference beam diffracted bythe master hologram to produce the initial set of fringes. Factors thatdetermine the net phase shift of each additional set of fringes withinthe HRM include: the thickness of the recording substrate, therefractive index of the recording substrate, the thickness of the masterhologram, the bandwidth of the master hologram, the angle of thereference beam diffracted by the master hologram to produce eachadditional set of fringes, and the wavelength of the reference beamdiffracted by the master hologram to produce each additional set offringes.

Control over the side lobes of a hologram may be achieved by controllingthe factors that determine the phase of the initial set of fringeswithin the HRM and by controlling the factors that determine the netphase shift of each set of additional fringes within the HRM. Thethickness of the recording substrate may be controlled by casting,milling, cutting, grinding, or otherwise producing a recording substratewith a desired thickness. The refractive index of the recordingsubstrate may be controlled by choosing a recording substrate materialwith a desired refractive index. The thickness of the master hologrammay be controlled by recording the master hologram in a HRM with adesired thickness. The bandwidth of the master hologram may becontrolled by controlling the thickness of the master hologram, wherethicker master holograms typically have a narrower bandwidth. Thebandwidth of the master hologram may be increased withbandwidth-broadening treatments. The angle of a reference beam may becontrolled by positioning the laser light source for a given referencebeam at a desired angle. The wavelength of a reference beam may becontrolled by choosing a laser light source with appropriate wavelengthoutputs; laser light sources with variable wavelength outputs may havetheir output wavelength determined by the conditions under which thevariable output laser light source is operated.

A hologram with apodized Δn will have side lobes with the leastmagnitude, and thereby comprises a hologram with controlled side lobes.A hologram with apodized Δn comprises a hologram wherein Δn is lowest atthe shallowest and deepest depth within the hologram and wherein Δn ishighest at a depth between the shallowest and deepest depth within thehologram. In other words, Δn is lowest at the first and second surfaceof the hologram and Δn is highest at a depth between the first andsecond surface. A hologram with anti-apodized Δn will have side lobeswith the greatest magnitude, and thereby comprises a hologram withcontrolled side lobes. A hologram with anti-apodized Δn comprises ahologram wherein Δn is highest at the shallowest and deepest depthwithin the hologram and wherein Δn is lowest at a depth between theshallowest and deepest depth within the hologram. In other words, Δn ishighest at the first and second surface of the hologram and Δn is lowestat a depth between the first and second surface.

Typically, a master hologram with a given thickness and bandwidth isused in combination with a recording substrate with a given thicknessand refractive index (in accordance with the present systems, devices,and methods). The wavelength and angle of the reference beam diffractedby the master hologram to produce the initial set of fringes within theHRM is fixed to achieve a desired playback wavelength and angle for therecorded hologram. The wavelength and angle of each reference beamdiffracted by the master hologram to record each additional set offringes is then fixed to achieve the necessary net phase shift for eachadditional set of fringes, such that the interference between theinitial set of fringes and each additional set of fringes within the HRMwill produce variations of Δn within the HRM that give the desiredmagnitude of side lobes relative to the main peak of the hologram withcontrolled side lobes.

A reference beam comprises laser light. A reference beam may comprise aplane wave, wherein a plane wave comprises laser light with parallelwave fronts. A plane wave does not converge to a point and a plane wavedoes not diverge from a point. A plane wave may be generated bycollimating laser light, wherein collimating laser light may includereflecting laser light with a mirror or refracting laser light with alens. A hologram recorded with a plane wave will have the most parallelfringes; in other words, the slant angle of the fringes will haveminimal change throughout the hologram. Recording a hologram with aplane wave may therefore be advantageous since the distribution of Δn asa function of depth within the resulting hologram will be the mostconsistent across the lateral dimensions of the hologram.

A reference beam may comprise a spherical wave, wherein a spherical wavecomprises laser light with spherically curved wave fronts; the curvatureof the wave fronts includes a focal point. A spherical wave eitherconverges to a focal point or diverges from a focal point. A sphericalwave may be generated by focusing laser light with a converging lens ora converging mirror; a spherical wave may be generated by defocusinglaser light with a diverging lens or a diverging mirror. Recording ahologram with a spherical wave may be advantageous since the recordedhologram will possess an optical power and therefore the recordedhologram may focus (or defocus) light in addition to any other opticalfunctions the recorded hologram performs. A hologram recorded with aspherical wave will not have perfectly parallel fringes; in other words,the slant angle of the fringes will not be exactly the same throughoutthe lateral dimensions of the hologram. However, the difference in slantangle between fringes does not affect the magnitude of the side lobes ofthe hologram so long as the focal point of the spherical wave(s) is(are) at a distance from the hologram equal to at least 50%, at least100%, or at least 200% of the largest lateral dimension of the hologramwith controlled side lobes. Increasing the focal distance (relative tothe size of the hologram) decreases the difference in slant anglebetween fringes, bringing the fringes of a hologram recorded with aspherical wave closer to parallel.

Consider FIG. 3A, which shows a cross-sectional view of hologram withunmatched fringe spacing 300 a in accordance with the present systems,devices, and methods. Hologram with unmatched fringe spacing 300 acomprises first set of fringes 310 a and second set of fringes 320 a,where the spacing of first set of fringes 310 a is less than the spacingof second set of fringes 320 a. Hologram with unmatched fringe spacing300 a comprises a hologram with anti-apodized Δn. Because the spacingsof first set of fringes 310 a and second set of fringes 320 a do notmatch, the depth of maximum constructive interference, and therefore thedepth of maximum Δn, will vary throughout the hologram laterally.

Consider FIG. 3B, which shows a cross-sectional view of hologram withunmatched phase 300 b in accordance with the present systems, devices,and methods. Hologram with unmatched phase 300 b comprises first set offringes 310 b and second set of fringes 320 b. The phase of first set offringes 310 b and second set of fringes 320 b combine such that firstset of fringes 310 b and second set of fringes 320 b interfereconstructively at the highest and lowest depth of hologram withunmatched phase 300 b and interfere destructively at the middle depth ofhologram with unmatched phase 300 b. Δn within hologram with unmatchedphase 300 b is therefore at a maximum at the highest and lowest depth ofhologram with unmatched phase 300 b and at a minimum at the middle depthof hologram with unmatched phase 300 b; hologram with unmatched phase300 b is therefore anti-apodized and would show the strongest possibleside lobes. This is advantageous if strong side lobes are desirable,however it is disadvantageous if minimal side lobes are desirable.Therefore, the phase of the diffracted object beams must be controlledduring replication.

Returning to FIG. 1, at 105, the hologram with controlled side lobes isdismounted from the recording substrate. Dis-mounting the hologram withcontrolled side lobes from the recording substrate includes physicallyde-coupling the hologram with controlled side lobes from the recordingsubstrate.

Method 100 may further comprise bleaching the hologram with controlledside lobes. Bleaching includes exposing the hologram with controlledside lobes to a bleaching agent. Non-exclusive examples of a bleachingagents include acids, peroxides, hypochlorites, and light.Photobleaching includes exposing the hologram with controlled side lobesto light. The light used for photobleaching may be incoherent. The lightused for photobleaching may be polychromatic, wherein at least a portionof the light which is used for photobleaching may be absorbed by thephotoinitiator or the monomer within the hologram with controlled sidelobes.

Photobleaching the hologram with controlled side lobes converts at leasta portion of the hologram with controlled side lobes from aphotopolymerizable material to a material that is notphotopolymerizable.

Method 100 may further comprise recording a master hologram. Recording amaster hologram may include illuminating a master HRM with an objectbeam and a reference beam.

FIG. 4 is a cross-sectional view of hologram with controlled side lobesrecording system 400 in accordance with the present systems, devices,and methods. Although FIG. 4 is a cross-sectional view, a dot-fillpattern has been used to differentiate various elements in FIG. 4 ratherthan a cross-hatch pattern to avoid confusion between the diagonal linesdenoting fringes and diagonal lines denoting cross-hatching.

Hologram with controlled side lobes recording system 400 comprises copyHRM 410, recording substrate 420, master hologram 430, laser lightsource 440, first reference beam 441, second reference beam 442, firstdiffracted object beam 443, and second diffracted object beam 444.Hologram with controlled side lobes recording system 400 may be employedto produce a hologram substantively similar to hologram with controlledside lobes 200 via method of producing a hologram with controlled sidelobes 100.

Copy HRM 410 comprises first copy HRM surface 411 and second copy HRMsurface 412. Recording substrate 420 comprises master-side surface 461and copy HRM-side surface 462. Master hologram 430 is physically coupledto master-side surface 461 of recording substrate 420, while first copyHRM surface 411 of copy HRM 410 is physically coupled to copy HRM-sidesurface 462 of recording substrate 420.

Laser light source 440 produces first reference beam 441 and secondreference beam 442. First reference beam 441 may be of a differentwavelength than second reference beam 442. First reference beam 441 maybe of a different angle than second reference beam 442. First referencebeam 441 and second reference beam 442 impinge on master hologram 430.Master hologram 430 comprises master hologram fringes 431. Masterhologram fringes 431 diffract first reference beam 441 and secondreference beam 442 to produce first diffracted object beam 443 andsecond diffracted object beam 444. Master hologram 430 produces firstdiffracted object beam 443 from first reference beam 441 and producessecond diffracted object beam 444 from second diffracted object beam444. First diffracted object beam 443 and first reference beam 441interfere to produce initial set of optical fringes 451. Seconddiffracted object beam 444 and second reference beam 442 interfere toproduce additional set of optical fringes 452.

Initial set of optical fringes 451 and additional set of optical fringes452 meta-interfere with each other within copy HRM 410. Constructivemeta-interference between initial set of optical fringes 451 andadditional set of optical fringes 452 causes an increase in Δn in thephysical fringes recorded from the optical fringes, while destructivemeta-interference between initial set of optical fringes 451 andadditional set of optical fringes 452 causes a decrease in Δn in thephysical fringes recorded from the optical fringes. The depth withincopy HRM 410 at which constructive or destructive meta-interferencebetween initial set of optical fringes 451 and additional set of opticalfringes 452 occurs depends on the phase of the initial set of opticalfringes 451 relative to the additional set of optical fringes 452.

First reference beam 441 will have a given phase at copy HRM-sidesurface 462. First diffracted object beam 443 will have a phase at copyHRM-side surface 462 that depends on the phase of first reference beam441 at copy HRM-side surface 462 and the effective distance travelled bythe light comprising first diffracted object beam 443. The effectivedistance travelled by the light comprising first diffracted object beam443 depends on the thickness and refractive index of recording substrate420. The difference in phase between first reference beam 441 and firstdiffracted object beam 443 at HRM-side surface 462 is the phase shift offirst diffracted object beam 443.

Second reference beam 442 will have a given phase at copy HRM-sidesurface 462. Second diffracted object beam 444 will have a phase at copyHRM-side surface 462 that depends on the phase of second reference beam442 at copy HRM-side surface 462 and the effective distance travelled bythe light comprising second diffracted object beam 444. The effectivedistance travelled by the light comprising second diffracted object beam444 depends on the thickness and refractive index of recording substrate420. The difference in phase between second reference beam 442 andsecond diffracted object beam 444 at HRM-side surface 462 is the phaseshift of second diffracted object beam 444.

The difference between the phase shift of second diffracted object beam444 and the phase shift of first diffracted object beam 443 is the netphase shift of second diffracted object beam 444. The phase of initialset of optical fringes 451 depends on the phase shift of firstdiffracted object beam 443. The phase of additional set of opticalfringes 452 depends on the phase shift of second diffracted object beam444. The difference in phase between additional set of optical fringes452 and initial set of optical fringes 451 is the net phase shift ofadditional set of optical fringes 452. The net phase shift of additionalset of optical fringes 452 depends on the net phase shift of seconddiffracted object beam 444.

The net phase shift of additional set of optical fringes 452 determinesthe location of constructive and destructive interference of initial setof optical fringes 451 and additional set of optical fringes 452. Thenet phase shift of additional set of optical fringes 452 may be measuredin radians at a depth within copy HRM 410 equidistant between first copyHRM surface 411 and second copy HRM surface 412. If the net phase shiftof additional set of optical fringes 452 is 0, then meta-interferencebetween initial set of optical fringes 451 and additional set of opticalfringes 452 will be most constructive at a depth within copy HRM 410equidistant between first copy HRM surface 411 and second copy HRMsurface 412 and most destructive at depths closest to first copy HRMsurface 411 and second copy HRM surface. If the net phase shift ofadditional set of optical fringes 452 is π, then meta-interferencebetween initial set of optical fringes 451 and additional set of opticalfringes 452 will be most destructive at a depth within copy HRM 410equidistant between first copy HRM surface 411 and second copy HRMsurface 412 and most constructive at depths closest to first copy HRMsurface 411 and second copy HRM surface.

If first reference beam 441 and the second reference beam 442 compriselight of differing angles with the same wavelength, first reference beam441 and second reference beam 442 will travel different paths to reachmaster hologram 430, and first diffracted object beam 443 and seconddiffracted object beam 444 will travel different paths to reach copy HRM410. The effective distance travelled by first diffracted object beam443 and second diffracted object beam 444 will be different. Theeffective distance travelled by first diffracted object beam 443 isequivalent to a first number of wavelengths of first diffracted objectbeam 443. The effective distance travelled by second diffracted objectbeam 444 is equivalent to a second number of wavelengths of seconddiffracted object beam 444. Due to the different effective distancestravelled, the first number of wavelengths of first diffracted objectbeam 443 is not equal to the second number of wavelengths of seconddiffracted object beam 444, and the difference between the first numberof wavelengths of first diffracted object beam 443 and the second numberof wavelengths of second diffracted object beam 444 is the net phaseshift of second diffracted object beam 444. The difference between thefirst number of wavelengths of first diffracted object beam 443 and thesecond number of wavelengths of second diffracted object beam 444depends on the thickness and the refractive index of recording substrate420 since the difference in effective distance travelled depends on thethickness of recording substrate 420. Therefore, the net phase shift ofsecond diffracted object beam 444 will be determined by the thicknessand refractive index of recording substrate 420.

If first reference beam 441 and the second reference beam 442 compriselight of differing wavelengths with the same angle, the net phase shiftof second diffracted object beam 444 will be determined by the thicknessand refractive index of recording substrate 420. First reference beam441 and second reference beam 442 will travel identical paths to reachmaster hologram 430, and first diffracted object beam 443 and seconddiffracted object beam 444 will travel identical paths to reach copy HRM410. The effective distance travelled by first diffracted object beam443 and second diffracted object beam 444 will be identical. Theeffective distance travelled by first diffracted object beam 443 isequivalent to a first number of wavelengths of first diffracted objectbeam 443. The effective distance travelled by second diffracted objectbeam 444 is equivalent to a second number of wavelengths of seconddiffracted object beam 444. The first number of wavelengths of firstdiffracted object beam 443 is not equal to the second number ofwavelengths of second diffracted object beam 444, and the differencebetween the first number of wavelengths of first diffracted object beam443 and the second number of wavelengths of second diffracted objectbeam 444 is the net phase shift of second diffracted object beam 444;the difference between the first number of wavelengths of firstdiffracted object beam 443 and the second number of wavelengths ofsecond diffracted object beam 444 depends on the thickness and therefractive index of recording substrate 420.

For a desired location of maximum constructive interference, a thicknessof recording substrate 420 may be calculated for the specificwavelengths of the first sub-beam of laser light and the second sub-beamof laser light at a given angle. In this manner, the phase of the lightcomprising initial set of optical fringes 451 and additional set ofoptical fringes 452 may be controlled; by extension the interferencebetween initial set of optical fringes 451 and additional set of opticalfringes 452 and thereby the location of maximum and minimum Δn may becontrolled.

In a preferred embodiment, hologram with controlled side lobes recordingsystem 400 comprising a first reference beam with an angle of 50 degreesand a wavelength of 455.0 nm, a second reference beam with an angle of50 degrees and a wavelength of 454.3 nm, a master hologram with aplayback angle of 0 degrees and a thickness of 20 micrometers, arecording substrate with a thickness of 57 um, and a copy HRM thicknessof 8 um will produce a copy HRM with the greatest magnitude of Δn at adepth equidistant from first copy HRM surface 411 and second copy HRMsurface 412, the least magnitude of Δn at first copy HRM surface 411 andsecond copy HRM surface 412, and side lobes with the least magnitude.

In an alternative embodiment, the parameters of the preferred embodimentare used with one modification chosen from a group consisting of:increasing the wavelength of the first reference beam by up to 0.1 nm,decreasing the wavelength of the first reference beam by up to 0.1 nm,increasing the wavelength of the second reference beam by up to 0.1 nm,decreasing the wavelength of the second reference beam by up to 0.1 nm,increasing the angle of the first reference beam and the secondreference beam each by up to 8 degrees, decreasing the angle of thefirst reference beam and the second reference beam each by up to 8degrees, increasing the master hologram playback angle by up to 8degrees, decreasing the master hologram playback angle by up to 8degrees, increasing the master thickness by up to 30 um, decreasing themaster thickness by up to 5 um, increasing the recording substratethickness by up to 9 um, decreasing the recording substrate thickness byup to 9 um, increasing the copy HRM thickness my 1 um, and decreasingthe copy HRM thickness by 1 um. The alternative embodiment will producea copy HRM with a magnitude of Δn at first copy HRM surface 411 andsecond copy HRM surface 412 less than or equal to 50% of the highestmagnitude of Δn within the copy HRM. A person of skill in the art ofholography will appreciate that if more than one of the modificationsdisclosed in the alternative embodiment are applied to the preferredembodiment, and the magnitude of each modification is greater than themagnitude of the modifications disclosed in the alternative embodiment,then a copy HRM with a magnitude of Δn at first copy HRM surface 411 andsecond copy HRM surface 412 less than or equal to 50% of the highestmagnitude of Δn within the copy HRM may be produced; the effect of eachmodification may at least partially counteract the effect of each othermodification.

Substantively similar control of the location of maximum and minimum Δnmay be achieved via control of the angles of the first sub-beam of laserlight and the second sub-beam of laser light. Substantively similarcontrol of the location of maximum and minimum Δn may be achieved viacontrol of the thickness of master hologram 430. Each fringe in themaster hologram diffracts the incoming laser light, at an angle suchthat the diffracted light interferes at least partially constructively.If the diffracted light is at an angle that results in interference thatis not completely constructive, then the interference is also partiallydestructive. The partially destructive interference decreases theamplitude of the diffracted laser light and simultaneously shifts thephase of the diffracted laser light. The magnitude of the decrease inamplitude and shift in phase is proportional to the number of fringesthat contribute to the partially destructive interference, which is inturn dependent on the thickness of the master hologram.

FIG. 4 depicts hologram with controlled side lobes recording system 400set up to replicate a reflection hologram since laser light source 440is located on the same side as copy HRM 410. A person of skill in theart will appreciate that hologram with controlled side lobes recordingsystem 400 may also be used to replicate a transmission hologram bymoving laser light source 440 to the same side as master hologram 430.

A person of skill in the art of holography will appreciate that whiletwo reference beams are produced by laser light 440 in FIG. 4, laserlight source 440 may alternatively produce 3, 4, or more referencebeams. Each additional reference beam (in other words, each referencebeam beyond the second) will have a wavelength and an angle, will passthrough the master hologram, the recording substrate, and the copy HRM,and produce a respective additional diffracted object beam that passesthrough the recording substrate and the copy HRM. Each additionaldiffracted object beam will possess a net phase shift and interfere witheach respective additional reference beam to produce a respectiveadditional set of optical fringes. Each additional set of opticalfringes will possess a respective net phase shift (determined by thewavelength and angle of the respective reference beam, the thickness andplayback angle of the master hologram, and the thickness of therecording substrate) and will meta-interfere with each other set ofoptical fringes to record a hologram with Δn varying as a function ofdepth. The presence of additional sets of meta-interfering opticalfringes allows more complex Δn profiles as a function of depth, allowinggreater control of the side lobes of the holograms recorded withhologram with controlled side lobes recording system 400.

FIG. 5 is a cross-sectional view of an exemplary eyeglass lens 500 withan embedded hologram with controlled side lobes 510 suitable for use asa transparent combiner in a WHUD in accordance with the present systems,devices, and methods. Eyeglass lens 500 with an embedded HOE 510comprises hologram with controlled side lobes 510 and lens assembly 520.Hologram with controlled side lobes 510 may be substantively similar tohologram with controlled side lobes 200. Hologram with controlled sidelobes 510 is embedded within an internal volume of lens assembly 520.Hologram with controlled side lobes 510 may be physically coupled tolens assembly 520 with a low-temperature optically clear adhesive(LT-OCA).

Hologram with controlled side lobes 510 comprises initial set of fringes511, additional set of fringes 512, first hologram surface 513, andsecond hologram surface 514. First hologram surface 513 is oppositesecond hologram surface 514. First hologram surface 513 and secondhologram surface 514 each comprise a two-dimensional surface; firsthologram surface 513 and second hologram surface 514 may compriseparallel surfaces. The distance between first hologram surface 513 andsecond hologram surface 514 is the thickness of hologram with controlledside lobes 510. Hologram with controlled side lobes 510 may be less thanten micrometers thick, less than 100 micrometers thick, or less than onemillimeter thick.

Initial set of fringes 511 and additional set of fringes 512 arecontained within an internal volume of hologram with controlled sidelobes 510. Initial set of fringes 511 possesses initial fringe spacing531 and initial fringe slant angle 541. Initial fringe spacing 531comprises the distance between one fringe comprising initial set offringes 511 and an immediately adjacent fringe comprising initial set offringes 511. Initial fringe spacing 531 may be measured parallel tofirst hologram surface 513 and/or second hologram surface 514. Initialfringe slant angle 541 comprises the angle between the fringescomprising initial set of fringes 511 and a line normal to at least oneof: first hologram surface 513 and second hologram surface 514.

Additional set of fringes 512 comprises additional fringe spacing 532,additional fringe slant angle 542, and net phase shift 550. Net phaseshift 550 comprises the difference in phase between initial set offringes 511 and additional set of fringes 512 at a depth equidistantbetween first hologram surface 513 and second hologram surface 514.Additional fringe spacing 532 comprises the distance between one fringecomprising additional set of fringes 512 and an immediately adjacentfringe comprising additional set of fringes 512. Additional fringespacing 532 may be measured parallel to first surface 513 and/or secondsurface 514. Additional fringe spacing 532 is equal to initial fringespacing 531. Additional fringe slant angle 542 comprises the anglebetween the fringes comprising additional set of fringes 512 and a linenormal to at least one of: first hologram surface 513 and secondhologram surface 514. Additional fringe slant angle 542 is not equal toinitial fringe slant angle 541.

Initial set of fringes 511 and additional set of fringes 512 exhibitmeta-interference. Portions of hologram with controlled side lobes 510that exhibit constructive meta-interference between initial set offringes 511 and additional set of fringes 512 possess higher Δn.Portions of hologram with controlled side lobes 510 that exhibitdestructive meta-interference between initial set of fringes 511 andadditional set of fringes 512 possess lower Δn. If Δn is least at depthsclosest to first surface 513 and/or second surface 514, and if Δn isgreatest at a depth equidistant from first hologram surface 513 andsecond hologram surface 514, then hologram with controlled side lobes510 will have side lobes with the least possible magnitude. If Δn atdepths closest to first hologram surface 513 and/or second hologramsurface 514 is less than 50% of Δn at a depth equidistant from firsthologram surface 513 and second hologram surface 514 then hologram withcontrolled side lobes 700 is at least partially apodized and may exhibitside lobes with an intensity less than 25%, less than 10%, or less thanone percent of the intensity of the primary peak.

If Δn is greatest at depths closest to first surface 513 and/or secondsurface 514, and if Δn is least at a depth equidistant from firsthologram surface 513 and second hologram surface 514, then hologram withcontrolled side lobes 510 will have side lobes with the greatestpossible magnitude. If Δn at a depth equidistant from first hologramsurface 513 and second hologram surface 514 is less than 50% of Δn atdepths closest to first hologram surface 513 and/or second hologramsurface 514 then hologram with controlled side lobes 510 is at leastpartially anti-apodized and will exhibit side lobes with an intensity atleast 25% of, at least 50% of, or greater than the intensity of theprimary peak.

If net phase shift 550 is equal to 0, then hologram with controlled sidelobes 510 will be apodized. If net phase shift 550 is equal to π, thenhologram with controlled side lobes 510 will be anti-apodized. A personof skill in the art of holography will appreciate that the position ofhighest Δn within hologram with controlled side lobes 510 depends on netphase shift 550, and since the magnitude of the side lobes of hologramwith controlled side lobes 510 depends on the position of highest Δn,the side lobes of hologram with controlled side lobes 510 may thereforebe controlled by controlling net phase shift 550. Control of net phaseshift 550 may be achieved by controlling the angle and wavelength of thereference beams used to record initial set of fringes 511 and additionalset of fringes 512.

A person of skill in the art of holography will appreciate that hologramwith controlled side lobes 510 may comprise more than one additional setof fringes; where each additional set of fringes comprises a respectiveadditional fringe spacing (equal to the initial fringe spacing),additional slant angle, and net phase shift. Each additional set offringes will also exhibit meta-interference with initial set of fringes511; hologram with controlled side lobes 510 would thereby possess amore complex distribution of Δn as a function of depth and greaterpossible control over the relative magnitude of the side lobes ofhologram with controlled side lobes 510.

Hologram with controlled side lobes 510 may comprise awavelength-multiplexed hologram, where initial set of fringes 511comprises at least two wavelength-specific sub-sets of fringes andadditional set of fringes 512 comprises at least two wavelength-specificsub-sets of fringes.

FIG. 6 is a partial-cutaway perspective view of a WHUD 600 that includesan eyeglass lens 630 with an embedded hologram with controlled sidelobes 631 in accordance with the present systems, devices, and methods.Eyeglass lens 630 may be substantially similar to eyeglass lens 500 fromFIG. 5. Embedded hologram with controlled side lobes 631 may besubstantively similar to hologram with controlled side lobes 200. WHUD600 comprises a support structure 610 that is worn on the head of theuser and has a general shape and appearance of an eyeglasses (e.g.,sunglasses) frame. Support structure 610 carries multiple components,including: an image source 620, and an eyeglass lens 630. Image source620 is positioned and oriented to direct light towards the eyeglass lensand may include, for example, a micro-display system, a scanning laserprojection system, or another system for generating display images. FIG.6 provides a partial-cutaway view in which regions of support structure610 have been removed in order to render visible portions of imagesource 620 and clarify the location of image source 620 within WHUD 600.Eyeglass lens 630 is positioned within a field of view of an eye of theuser when the support structure is worn on the head of the user andserves as both a conventional eyeglass lens (i.e., prescription ornon-prescription depending on the needs of the user) and a transparentcombiner.

Eyeglass lens 630 with an embedded hologram with controlled side lobes631 comprises hologram with controlled side lobes 631 and lens assembly632. Hologram with controlled side lobes 631 is embedded within aninternal volume of lens assembly 632. Hologram with controlled sidelobes 631 may be physically coupled to lens assembly 632 with alow-temperature optically clear adhesive (LT-OCA).

Hologram with controlled side lobes 631 comprises initial set of fringes633, additional set of fringes 634, first hologram surface 635, andsecond hologram surface 636. First hologram surface 635 is oppositesecond hologram surface 636. First hologram surface 635 and secondhologram surface 636 each comprise a two-dimensional surface; firsthologram surface 635 and second hologram surface 636 may compriseparallel surfaces. The distance between first hologram surface 635 andsecond hologram surface 636 is the thickness of hologram with controlledside lobes 631. Hologram with controlled side lobes 631 may be less thanten micrometers thick, less than 100 micrometers thick, or less than onemillimeter thick.

Initial set of fringes 633 and additional set of fringes 634 arecontained within an internal volume of hologram with controlled sidelobes 631. Initial set of fringes 633 possesses initial fringe spacing641 and initial fringe slant angle 643. Initial fringe spacing 641comprises the distance between one fringe comprising initial set offringes 633 and an immediately adjacent fringe comprising initial set offringes 633. Initial fringe spacing 641 may be measured parallel tofirst hologram surface 635 and/or second hologram surface 636. Initialfringe slant angle 643 comprises the angle between the fringescomprising initial set of fringes 633 and a line normal to at least oneof: first hologram surface 635 and second hologram surface 636.

Additional set of fringes 634 comprises additional fringe spacing 642,additional fringe slant angle 644, and net phase shift 645. Net phaseshift 645 comprises the difference in phase between initial set offringes 633 and additional set of fringes 634 at a depth equidistantbetween first hologram surface 635 and second hologram surface 636.Additional fringe spacing 642 comprises the distance between one fringecomprising additional set of fringes 634 and an immediately adjacentfringe comprising additional set of fringes 634. Additional fringespacing 642 may be measured parallel to first surface 635 and/or secondsurface 636. Additional fringe spacing 642 is equal to initial fringespacing 641. Additional fringe slant angle 644 comprises the anglebetween the fringes comprising additional set of fringes 634 and a linenormal to at least one of: first hologram surface 635 and secondhologram surface 636. Additional fringe slant angle 644 is not equal toinitial fringe slant angle 643.

Initial set of fringes 633 and additional set of fringes 634 exhibitmeta-interference. Portions of hologram with controlled side lobes 631that exhibit constructive meta-interference between initial set offringes 633 and additional set of fringes 634 possess higher Δn.Portions of hologram with controlled side lobes 631 that exhibitdestructive meta-interference between initial set of fringes 633 andadditional set of fringes 634 possess lower Δn. If Δn is least at depthsclosest to first surface 635 and/or second surface 636, and if Δn isgreatest at a depth equidistant from first hologram surface 635 andsecond hologram surface 636, then hologram with controlled side lobes631 will have side lobes with the least possible magnitude. If Δn atdepths closest to first hologram surface 635 and/or second hologramsurface 636 is less than 50% of Δn at a depth equidistant from firsthologram surface 635 and second hologram surface 636 then hologram withcontrolled side lobes 631 is at least partially apodized and may exhibitside lobes with an intensity less than 25%, less than 10%, or less thanone percent of the intensity of the primary peak.

If Δn is greatest at depths closest to first surface 635 and/or secondsurface 636, and if Δn is least at a depth equidistant from firsthologram surface 635 and second hologram surface 636, then hologram withcontrolled side lobes 631 will have side lobes with the greatestpossible magnitude. If Δn at a depth equidistant from first hologramsurface 635 and second hologram surface 636 is less than 50% of Δn atdepths closest to first hologram surface 635 and/or second hologramsurface 636 then hologram with controlled side lobes 631 is at leastpartially anti-apodized and will exhibit side lobes with an intensity atleast 25% of, at least 50% of, or greater than the intensity of theprimary peak.

If net phase shift 645 is equal to 0, then hologram with controlled sidelobes 631 will be apodized. If net phase shift 645 is equal to π, thenhologram with controlled side lobes 631 will be anti-apodized. A personof skill in the art of holography will appreciate that the position ofhighest Δn within hologram with controlled side lobes 631 depends on netphase shift 645, and since the magnitude of the side lobes of hologramwith controlled side lobes 631 depends on the position of highest Δn,the side lobes of hologram with controlled side lobes 631 may thereforebe controlled by controlling net phase shift 645. Control of net phaseshift 645 may be achieved by controlling the angle and wavelength of thereference beams used to record initial set of fringes 633 and additionalset of fringes 634.

A person of skill in the art of holography will appreciate that hologramwith controlled side lobes 631 may comprise more than one additional setof fringes; where each additional set of fringes comprises a respectiveadditional fringe spacing (equal to the initial fringe spacing),additional slant angle, and net phase shift. Each additional set offringes will also exhibit meta-interference with initial set of fringes633; hologram with controlled side lobes 631 would thereby possess amore complex distribution of Δn as a function of depth and greaterpossible control over the relative magnitude of the side lobes ofhologram with controlled side lobes 631.

Hologram with controlled side lobes 631 may comprise awavelength-multiplexed hologram, where initial set of fringes 633comprises at least two wavelength-specific sub-sets of fringes andadditional set of fringes 634 comprises at least two wavelength-specificsub-sets of fringes.

FIG. 7 is a cross-sectional view of hologram with controlled side lobes700 in accordance with the present systems, devices, and methods.Hologram with controlled side lobes 700 is substantively similar tohologram with controlled side lobes 200. Hologram with controlled sidelobes 700 may be produced by method 100. Hologram with controlled sidelobes 700 comprises initial set of fringes 710, additional set offringes 720, first surface 731, and second surface 732.

First surface 731 is opposite second surface 732. First surface 731 andsecond surface 732 each comprise a two-dimensional surface. Hologramwith controlled side lobes 700 occupies the volume between first surface731 and second surface 732. First surface 731 and second surface 732 areseparated by thickness 733 wherein thickness 733 comprises the shortestdistance between first surface 731 and second surface 732 at a givenpoint on or within hologram with controlled side lobes 700. Thickness733 may be less than ten micrometers, less than one hundred micrometers,or less than one millimeter.

First surface 731 may comprise a curved surface; first surface 731 maybe curved spherically or cylindrically around a focal point or focalline, respectively. Second surface 732 may comprise a curved surface;second surface 732 may be curved spherically or cylindrically around afocal point or focal line, respectively. First surface 731 and secondsurface 732 may comprise parallel surfaces.

Initial set of fringes 710 is located within an internal volume ofhologram with controlled side lobes 700. For the sake of clarity,initial set of fringes 710 has been depicted as a series of lines, wherethe lines denote the spacing between fringes. A person of skill in theart of holography will appreciate that fringes may comprise local maxima(or minima) of either absorbance or refractive index, and these maxima(or minima) may not show sharp boundaries between regions of high (orlow) absorbance or refractive index; however, the maxima (or minima) ofeither absorbance or refractive index demonstrate directionality andperiodicity and may be reasonably depicted and interpreted as arepeating pattern of discrete lines.

Initial set of fringes 710 comprises initial fringe phase 741, initialfringe spacing 751, and initial fringe slant angle 761. Initial fringephase 741 is depicted as being measured from the lateral edge ofhologram with controlled side lobes 700 to a particular fringe ofinitial set of fringes 710 at a depth equidistant between first surface731 and second surface 732, however a person of skill in the art ofholography will appreciate that, due to the periodic nature of thefringes comprising initial set of fringes 710, initial fringe phase 741could be measured from any fixed point in or on hologram with controlledside lobes 700 to any fringe of initial set of fringes 710.

Initial fringe spacing 751 comprises the distance between one fringecomprising initial set of fringes 710 and an immediately adjacent fringecomprising initial set of fringes 710. Initial fringe spacing 751 may bemeasured parallel to first surface 731 and/or second surface 732.Initial fringe spacing 751 at least partially determines the wavelengthor range of wavelengths of incident light that may be diffracted byinitial set of fringes 710; in other words, initial fringe spacing 751at least partially determines the wavelength(s) of light that may beused as an object beam to play back the hologram which initial set offringes 710 comprises.

Initial fringe slant angle 761 comprises the angle between the fringescomprising initial set of fringes 710 and a line normal to at least oneof: first surface 731 and second surface 732. In other words, if thefringes comprising initial set of fringes 710 are parallel to firstsurface 731 then the fringes comprising initial set of fringes 710 wouldhave a slant angle of 90 degrees. If the laser light used to recordinitial set of fringes 710 consists of plane waves then initial fringeslant angle 761 will be constant throughout hologram with controlledside lobes 700. If the laser light used to record initial set of fringes710 comprises spherical waves then initial fringe slant angle 761 willvary throughout hologram with controlled side lobes 700; however, thevariation in slant angle caused by spherical waves is negligible withregard to controlling the distribution of Δn, and thereby controllingthe sidelobes of hologram with controlled sidelobes 700, so long as thefocal point of each spherical wave is located at a distance equal to atleast 50%, at least 100%, or at least 200% of the largest lateraldimension of hologram with controlled side lobes 700.

Additional set of fringes 720 is located within an internal volume ofhologram with controlled side lobes 700. For the sake of clarity,additional set of fringes 720 has been depicted as a series of lines,where the lines denote the angle, phase, and the spacing betweenfringes. Additional set of fringes 720 comprises net phase shift 742,additional fringe spacing 752, and additional fringe slant angle 762.Net phase shift 742 comprises the difference in phase between initialset of fringes 710 and additional set of fringes 720 at a depthequidistant between first surface 731 and second surface 732. Net phaseshift 742 is depicted as being measured between a particular fringe ofadditional set of fringes 720 and a particular fringe of initial set offringes 710, however a person of skill in the art of holography willappreciate that, due to the periodic nature of the fringes comprisingadditional set of fringes 720, net phase shift 742 could be measuredfrom any fringe of initial set of fringes 710 to any fringe ofadditional set of fringes 720. Additional fringe spacing 752 comprisesthe distance between one fringe comprising additional set of fringes 720and an immediately adjacent fringe comprising additional set of fringes720.

Additional fringe spacing 752 may be measured parallel to first surface731 and/or second surface 732. Additional fringe spacing 752 at leastpartially determines the wavelength or range of wavelengths of incidentlight that may be diffracted by additional set of fringes 720; in otherwords, additional fringe spacing 752 at least partially determines thewavelength(s) of light that may be used as an object beam to play backthe hologram which additional set of fringes 720 comprises. Additionalfringe spacing 752 is equal to initial fringe spacing 751.

Additional fringe slant angle 762 comprises the angle between thefringes comprising additional set of fringes 720 and a line normal to atleast one of: first surface 731 and second surface 732. If the laserlight used to record additional set of fringes 720 consists of planewaves then additional fringe slant angle 762 will be constant throughouthologram with controlled side lobes 700. If the laser light used torecord additional set of fringes 720 comprises spherical waves thenadditional fringe slant angle 762 will vary throughout hologram withcontrolled side lobes 700; however, the variation in slant angle causedby spherical waves is negligible with regard to controlling thedistribution of Δn, and thereby controlling the sidelobes of hologramwith controlled sidelobes 700, so long as the focal point of eachspherical wave is located at a distance equal to at least 50%, at least100%, or at least 200% of the largest lateral dimension of hologram withcontrolled side lobes 700. Additional fringe slant angle 762 is notequal to initial fringe slant angle 761.

Initial set of fringes 710 and additional set of fringes 720 exhibitmeta-interference. Portions of hologram with controlled side lobes 700that exhibit constructive meta-interference between initial set offringes 710 and additional set of fringes 720 possess higher Δn.Portions of hologram with controlled side lobes 700 that exhibitdestructive meta-interference between initial set of fringes 710 andadditional set of fringes 720 possess lower Δn. If Δn is least at depthsclosest to first surface 731 and/or second surface 732, and if Δn isgreatest at a depth equidistant from first surface 731 and secondsurface 732, then hologram with controlled side lobes 700 will have sidelobes with the least possible magnitude; in other words hologram withcontrolled side lobes 700 is apodized. If Δn at depths closest to firstsurface 731 and/or second surface 732 is less than 50% of Δn at a depthequidistant from first surface 731 and second surface 732 then hologramwith controlled side lobes 700 is at least partially apodized and mayexhibit side lobes with an intensity less than 25%, less than 10%, orless than one percent of the intensity of the primary peak.

If Δn is greatest at depths closest to first surface 731 and/or secondsurface 732, and if Δn is least at a depth equidistant from firstsurface 731 and second surface 732, then hologram with controlled sidelobes 700 will have side lobes with the greatest possible magnitude; inother words, hologram with controlled side lobes 700 is anti-apodized.Higher Δn at first surface 731 and second surface 732 increases themagnitude of the side lobes, while higher Δn at a point equidistantbetween first surface 731 and second surface 732 increases the magnitudeof the primary peak. If Δn at a depth equidistant from first surface 731and second surface 732 is less than 50% of Δn at depths closest to firstsurface 731 and/or second surface 732 then hologram with controlled sidelobes 700 is at least partially anti-apodized and will exhibit sidelobes with an intensity at least 25% of, at least 50% of, or greaterthan the intensity of the primary peak.

Net phase shift 742 may be expressed in units of radians, where a phaseshift of 2π is equal to a phase shift of 0. If net phase shift 742 isequal to 0, then hologram with controlled side lobes 700 will beapodized. If net phase shift 742 is equal to π, then hologram withcontrolled side lobes 700 will be anti-apodized. A person of skill inthe art of holography will appreciate that the position of highest Δnwithin hologram with controlled side lobes 700 depends on net phaseshift 742, and since the magnitude of the side lobes of hologram withcontrolled side lobes 700 depends on the position of highest Δn, theside lobes of hologram with controlled side lobes 700 may therefore becontrolled by controlling net phase shift 742. Control of net phaseshift 742 may be achieved by controlling the angle and wavelength of thereference beams used to record initial set of fringes 710 and additionalset of fringes 720.

Any increase in Δn as a function of depth within hologram withcontrolled side lobes 700 will be a continuous increase if only two setsof fringes are present in hologram with controlled side lobes 700. Anydecrease in Δn as a function of depth within hologram with controlledside lobes 700 will be a continuous decrease if only two sets of fringesare present in hologram with controlled side lobes 700. More complexvariation in Δn as a function of depth within hologram with controlledside lobes 700 requires more than two sets of fringes within hologramwith controlled side lobes 700.

A person of skill in the art of holography will appreciate that hologramwith controlled side lobes 700 may comprise more than one additional setof fringes; where each additional set of fringes comprises a respectiveadditional fringe spacing (equal to the initial fringe spacing),additional slant angle, and net phase shift. Each additional set offringes will also exhibit meta-interference with initial set of fringes710; hologram with controlled side lobes 700 would thereby possess amore complex distribution of Δn as a function of depth and greaterpossible control over the relative magnitude of the side lobes ofhologram with controlled side lobes 700.

Hologram with controlled side lobes 700 may comprise awavelength-multiplexed hologram, where initial set of fringes 710comprises at least two wavelength-specific sub-sets of fringes andadditional set of fringes 720 comprises at least two wavelength-specificsub-sets of fringes. A wavelength-specific sub-set of fringes diffractslaser light with a range of wavelengths that is at least partiallydifferent from the range of wavelengths diffracted by each otherwavelength-specific sub-set of fringes. Hologram with controlled sidelobes 700 may comprise a red hologram, a green hologram, a bluehologram, and an infrared hologram, where each color of hologramcorresponds to a respective initial wavelength-specific sub-set ofinitial and additional fringes.

The intensity of the side lobes of a hologram may be measured relativeto the intensity of the primary peak of the hologram. Relative to theprimary peak of the hologram, the intensity of the side lobes of theblue hologram, the green hologram, the red hologram, and the infraredhologram may be equal. Due to the large difference in wavelength betweeneach color hologram, careful selection of wavelength and angle isrequired for each reference beam employed in the production of hologramwith controlled side lobes 700 to ensure that each color hologram hasthe same net phase shift when recorded on a recording substrate with aconstant thickness.

FIG. 8 is a cross-sectional view of an exemplary eyeglass lens 800 withcomprising a light guide and a hologram with controlled side lobes inaccordance with the present systems, devices, and methods. Eyeglass lens800 comprises light guide 810, in-coupler 811, out-coupler 812, claddinglayer 818 and lens layer 819.

Cladding layer 818 surrounds light guide 810, in-coupler 811, andGRIN-outcoupler 812. Cladding layer 818 comprises a low index material,where cladding layer may comprise a material with a refractive index of1.5, 1.2, or 1.0. A lower refractive index is more advantageous as thisincreases the field of view of the light guide when the light guide isused as a display. A non-exclusive example of a cladding material with arefractive index of 1.5 is a plastic material (PET, acrylic, Nylon,etc.). A non-exclusive example of a cladding material with a refractiveindex of 1.2 is a layer of silica sol-gel. A non-exclusive example of acladding material with a refractive index of 1.0 is air, where acladding layer comprising air typically includes additional material toprovide structural support to the light guide.

In-coupler 811 comprises first surface 813 and third surface 815.In-coupler 811 is physically coupled to light guide 810 at first surface813; in-coupler 811 is positioned and oriented to redirect light intolight guide 810. Out-coupler 812 comprises second surface 814 and fourthsurface 816. Out-coupler 812 is physically coupled to light guide 810 atsecond surface 814; out-coupler 812 is positioned and oriented toredirect light out of light guide 810.

Beam of light 820 impinges on in-coupler 811 with incident angle 823 andis redirected into light guide 810 at an angle greater than the criticalangle for light guide 810. Beam of light 820 is diffracted by incoupler811 and is converted to guided light 821. Guided light 821 propagatesthrough light guide 810 at an angle greater than the critical angle,bouncing off of the opposed surfaces of light guide 810 due to totalinternal reflection (TIR). Upon reaching out-coupler 812, guided light821 is redirected out of light guide 810 to form redirected light 822;redirected light 822 is directed towards an eye of a user 813.

Eyeglass lens 800 may further comprise exit pupil expander 817; exitpupil expander 817 may be physically coupled to light guide 810. Exitpupil expander 817 may replicate guided light 821 to form additionalbeams of light, where the additional beams of light propagate to theoutcoupler and may be redirected out of light guide 810 towards an eyeof a user 813, expanding the eyebox of eyeglass lens 800 when eyeglasslens 800 is utilized in a wearable heads-up display. Light guide 810 mayadvantageously comprise a high index material.

Each of: in-coupler 811, out-coupler 812, and/or exit pupil expander817, may comprise a hologram with controlled side lobes substantivelysimilar to hologram with controlled side lobes 200. Eyeglass lens 800may be similar in some ways to eyeglass lens 500. Eyeglass lens 800 maysimilar in some ways to eyeglass lens 630.

A person of skill in the art will appreciate that the variousembodiments for side lobe control in holograms described herein may beapplied in non-WHUD applications. For example, the present systems,devices, and methods may be applied in non-wearable heads-up displaysand/or in other applications that may or may not include a visibledisplay.

In some implementations, one or more optical fiber(s) may be used toguide light signals along some of the paths illustrated herein.

The WHUDs described herein may include one or more sensor(s) (e.g.,microphone, camera, thermometer, compass, altimeter, and/or others) forcollecting data from the user's environment. For example, one or morecamera(s) may be used to provide feedback to the processor of the WHUDand influence where on the display(s) any given image should bedisplayed.

The WHUDs described herein may include one or more on-board powersources (e.g., one or more battery(ies)), a wireless transceiver forsending/receiving wireless communications, and/or a tethered connectorport for coupling to a computer and/or charging the one or more on-boardpower source(s).

The WHUDs described herein may receive and respond to commands from theuser in one or more of a variety of ways, including without limitation:voice commands through a microphone; touch commands through buttons,switches, or a touch sensitive surface; and/or gesture-based commandsthrough gesture detection systems as described in, for example, U.S.Non-Provisional patent application Ser. No. 14/155,087, U.S.Non-Provisional patent application Ser. No. 14/155,107, PCT PatentApplication PCT/US2014/057029, and/or U.S. Provisional PatentApplication Ser. No. 62/236,060, all of which are incorporated byreference herein in their entirety.

Throughout this specification and the appended claims the term“communicative” as in “communicative pathway,” “communicative coupling,”and in variants such as “communicatively coupled,” is generally used torefer to any engineered arrangement for transferring and/or exchanginginformation. Exemplary communicative pathways include, but are notlimited to, electrically conductive pathways (e.g., electricallyconductive wires, electrically conductive traces), magnetic pathways(e.g., magnetic media), and/or optical pathways (e.g., optical fiber),and exemplary communicative couplings include, but are not limited to,electrical couplings, magnetic couplings, and/or optical couplings.

Throughout this specification and the appended claims, infinitive verbforms are often used. Examples include, without limitation: “to detect,”“to provide,” “to transmit,” “to communicate,” “to process,” “to route,”and the like. Unless the specific context requires otherwise, suchinfinitive verb forms are used in an open, inclusive sense, that is as“to, at least, detect,” to, at least, provide,” “to, at least,transmit,” and so on.

The above description of illustrated embodiments, including what isdescribed in the Abstract, is not intended to be exhaustive or to limitthe embodiments to the precise forms disclosed. Although specificembodiments of and examples are described herein for illustrativepurposes, various equivalent modifications can be made without departingfrom the spirit and scope of the disclosure, as will be recognized bythose skilled in the relevant art. The teachings provided herein of thevarious embodiments can be applied to other portable and/or wearableelectronic devices, not necessarily the exemplary wearable electronicdevices generally described above.

For instance, the foregoing detailed description has set forth variousembodiments of the devices and/or processes via the use of blockdiagrams, schematics, and examples. Insofar as such block diagrams,schematics, and examples contain one or more functions and/oroperations, it will be understood by those skilled in the art that eachfunction and/or operation within such block diagrams, flowcharts, orexamples can be implemented, individually and/or collectively, by a widerange of hardware, software, firmware, or virtually any combinationthereof. In one embodiment, the present subject matter may beimplemented via Application Specific Integrated Circuits (ASICs).However, those skilled in the art will recognize that the embodimentsdisclosed herein, in whole or in part, can be equivalently implementedin standard integrated circuits, as one or more computer programsexecuted by one or more computers (e.g., as one or more programs runningon one or more computer systems), as one or more programs executed by onone or more controllers (e.g., microcontrollers) as one or more programsexecuted by one or more processors (e.g., microprocessors, centralprocessing units, graphical processing units), as firmware, or asvirtually any combination thereof, and that designing the circuitryand/or writing the code for the software and or firmware would be wellwithin the skill of one of ordinary skill in the art in light of theteachings of this disclosure.

When logic is implemented as software and stored in memory, logic orinformation can be stored on any processor-readable medium for use by orin connection with any processor-related system or method. In thecontext of this disclosure, a memory is a processor-readable medium thatis an electronic, magnetic, optical, or other physical device or meansthat contains or stores a computer and/or processor program. Logicand/or the information can be embodied in any processor-readable mediumfor use by or in connection with an instruction execution system,apparatus, or device, such as a computer-based system,processor-containing system, or other system that can fetch theinstructions from the instruction execution system, apparatus, or deviceand execute the instructions associated with logic and/or information.

In the context of this specification, a “non-transitoryprocessor-readable medium” can be any element that can store the programassociated with logic and/or information for use by or in connectionwith the instruction execution system, apparatus, and/or device. Theprocessor-readable medium can be, for example, but is not limited to, anelectronic, magnetic, optical, electromagnetic, infrared, orsemiconductor system, apparatus or device. More specific examples (anon-exhaustive list) of the computer readable medium would include thefollowing: a portable computer diskette (magnetic, compact flash card,secure digital, or the like), a random access memory (RAM), a read-onlymemory (ROM), an erasable programmable read-only memory (EPROM, EEPROM,or Flash memory), a portable compact disc read-only memory (CDROM),digital tape, and other non-transitory media.

The various embodiments described above can be combined to providefurther embodiments. To the extent that they are not inconsistent withthe specific teachings and definitions herein, all of the U.S. patents,U.S. patent application publications, U.S. patent applications, foreignpatents, foreign patent applications and non-patent publicationsreferred to in this specification and/or listed in the Application DataSheet which are owned by Thalmic Labs Inc., including but not limitedto: US Patent Publication No. US 2015-0378161 A1, U.S. Non-Provisionalpatent application Ser. No. 15/046,234, U.S. Non-Provisional patentapplication Ser. No. 15/046,254, U.S. Non-Provisional patent applicationSer. No. 15/046,269, U.S. Provisional Patent Application Ser. No.62/156,736, U.S. Provisional Patent Application Ser. No. 62/214,600,U.S. Provisional Patent Application Ser. No. 62/167,767, U.S.Provisional Patent Application Ser. No. 62/271,135, U.S. ProvisionalPatent Application Ser. No. 62/245,792, U.S. Non-Provisional patentapplication Ser. No. 14/155,087, U.S. Non-Provisional patent applicationSer. No. 14/155,107, PCT Patent Application PCT/US2014/057029, and/orU.S. Provisional Patent Application Ser. No. 62/236,060, US PatentApplication Publication No. US 2017-0068095 A1; US Patent ApplicationPublication No. US 2017-0212290 A1; U.S. Provisional Patent ApplicationSer. No. 62/482,062; U.S. Provisional Patent Application Ser. No.62/534,099, U.S. Provisional Patent Application Ser. No. 62/557,551,U.S. Provisional Patent Application Ser. No. 62/557,554, U.S.Provisional Patent Application Ser. No. 62/565,677, U.S. ProvisionalPatent Application Ser. No. 62/631,278, and U.S. Provisional PatentApplication Ser. No. 62/664,758 are incorporated herein by reference, intheir entirety. Aspects of the embodiments can be modified, ifnecessary, to employ systems, circuits and concepts of the variouspatents, applications and publications to provide yet furtherembodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

1. A hologram with controlled side lobes comprising: a first surface; asecond surface opposite the first surface; an initial set of fringeswithin the volume of the hologram, the initial set of fringes comprisingan initial fringe phase, an initial fringe spacing and an initial fringeslant angle; and at least one additional set of fringes within thevolume of the hologram, wherein each additional set of fringes comprisesa respective net phase shift relative to the phase of the initial set offringes, an additional fringe spacing, and an additional fringe slantangle wherein each additional fringe spacing is equal to the initialfringe spacing, each additional fringe slant angle is not equal to theinitial fringe slant angle or any other additional fringe slant angle,the initial set of fringes and all additional sets of fringesmeta-interfere, and the magnitude of Δn within the hologram variesbetween the first surface and the second surface.
 2. The hologram ofclaim 1 wherein the intensity of each of the side lobes is less than onepercent of the intensity of the primary hologram peak.
 3. The hologramof claim 1 wherein the intensity of at least one of the side lobes isgreater than the intensity of the primary hologram peak.
 4. The hologramof claim 1 wherein: the initial set of fringes and each additional setof fringes meta-interfere most constructively at a depth through thehologram between the first surface and the second surface; the initialset of fringes and each additional set of fringes meta-interfere atleast partially destructively at the first surface; the initial set offringes and each additional set of fringes meta-interfere at leastpartially destructively at the second surface; the magnitude of Δn atthe first surface is equal to or less than 50% of the greatest magnitudeof Δn within the hologram; and the magnitude of Δn at the second surfaceis equal to or less than 50% of the greatest magnitude of Δn within thehologram.
 5. The hologram of claim 4 wherein the magnitude of Δnincreases continuously from the first surface to the maximum value of Δnwithin the hologram and the magnitude of Δn increases continuously fromthe second surface to the maximum value of Δn within the hologram. 6.The hologram of claim 1 wherein: the initial set of fringes and eachadditional set of fringes meta-interfere most destructively at a depththrough the hologram between the first surface and the second surface;the initial set of fringes and each additional set of fringesmeta-interfere at least partially constructively at the first surface;the initial set of fringes and each additional set of fringesmeta-interfere at least partially constructively at the second surface;at least one of: the first surface and the second surface possess thegreatest magnitude of Δn; the minimum magnitude of Δn within the volumeof the hologram is no greater than 50% of the greatest magnitude of Δnwithin the hologram; and the magnitude of Δn decreases continuously fromthe first surface to the minimum value of Δn within the hologram and themagnitude of Δn decreases continuously from the second surface to theminimum value of Δn within the hologram.
 7. The hologram of claim 1wherein the hologram comprises a wavelength-multiplexed hologram.
 8. Thehologram of claim 7 wherein the wavelength-multiplexed hologramcomprises a blue hologram, a green hologram, a red hologram, and aninfrared hologram.
 9. The hologram of claim 8 wherein: the intensity ofthe side lobes of the blue hologram relative to the intensity of primarypeak of the blue hologram is equal to the intensity of the side lobes ofthe green hologram relative to the intensity of primary peak of thegreen hologram; the intensity of the side lobes of the green hologramrelative to the intensity of primary peak of the green hologram is equalto the intensity of the side lobes of the red hologram relative to theintensity of primary peak of the red hologram; and the intensity of theside lobes of the red hologram relative to the intensity of primary peakof the red hologram is equal to the intensity of the side lobes of theinfrared hologram relative to the intensity of primary peak of theinfrared hologram.
 10. An eyeglass lens for use in a wearable heads-updisplay, the eyeglass lens comprising: a hologram with controlled sidelobes comprising: a first surface; a second surface opposite the firstsurface; an initial set of fringes within the volume of the hologramcomprising an initial fringe spacing and an initial slant angle; and atleast one additional set of fringes within the volume of the hologram,wherein each additional set of fringes comprises a respective net phaseshift relative to the phase of the initial set of fringes, an additionalfringe spacing, and an additional fringe slant angle wherein eachadditional fringe spacing is equal to the initial fringe spacing, eachadditional fringe slant angle is not equal to the initial fringe slantangle or any other additional fringe slant angle, the initial set offringes and all additional sets of fringes meta-interfere, and themagnitude of Δn within the hologram varies between the first surface andthe second surface; and at least one lens portion, wherein each lensportion is physically coupled to the hologram with controlled sidelobes.
 11. The lens of claim 10 wherein the intensity of each of theside lobes of the hologram is less than one percent of the intensity ofthe primary hologram peak.
 12. The lens of claim 10 wherein theintensity of at least one of the side lobes of the hologram is greaterthan the intensity of the primary hologram peak.
 13. The lens of claim10 wherein the initial set of fringes and each additional set of fringesmeta-interfere most constructively at a depth through the hologrambetween the first surface and the second surface; the initial set offringes and each additional set of fringes meta-interfere at leastpartially destructively at the first surface; the initial set of fringesand each additional set of fringes meta-interfere at least partiallydestructively at the second surface; the magnitude of Δn at the firstsurface is equal to or less than 50% of the greatest magnitude of Δnwithin the hologram; and the magnitude of Δn at the second surface isequal to or less than 50% of the greatest magnitude of Δn within thehologram.
 14. The lens of claim 10 wherein the initial set of fringesand each additional set of fringes meta-interfere most destructively ata depth through the hologram between the first surface and the secondsurface; the initial set of fringes and each additional set of fringesmeta-interfere at least partially constructively at the first surface;the initial set of fringes and each additional set of fringesmeta-interfere at least partially constructively at the second surface;at least one of: the first surface and the second surface possess thegreatest magnitude of Δn; the minimum magnitude of Δn within the volumeof the hologram is no greater than 50% of the greatest magnitude of Δnwithin the hologram; and the magnitude of Δn decreases continuously fromthe first surface to the minimum value of Δn within the hologram and themagnitude of Δn decreases continuously from the second surface to theminimum value of Δn within the hologram.
 15. The lens of claim 10wherein the hologram comprises a wavelength-multiplexed hologram, thewavelength-multiplexed hologram comprising a blue hologram, a greenhologram, a red hologram, and an infrared hologram.
 16. A wearableheads-up display comprising: a support structure; a projector; and atransparent combiner positioned and oriented to appear in a field ofview of an eye of a user when the support structure is worn on a head ofthe user, the transparent combiner comprising: a hologram withcontrolled side lobes comprising: a first surface; a second surfaceopposite the first surface; an initial set of fringes within the volumeof the hologram comprising an initial fringe spacing and an initialslant angle; and at least one additional set of fringes within thevolume of the hologram, wherein each additional set of fringes comprisesa given additional fringe spacing and a given additional slant anglewherein each additional fringe spacing is equal to the initial fringespacing, each additional slant angle is not equal to the initial slantangle or any other additional slant angle, the initial set of fringesand all additional sets of fringes meta-interfere, and the magnitude ofΔn within the hologram varies between the first surface and the secondsurface; and at least one lens portion, wherein each lens portion isphysically coupled to the hologram with controlled side lobes.
 17. Thewearable heads-up display of claim 16 wherein the intensity of each ofthe side lobes of the hologram is less than one percent of the intensityof the primary hologram peak.
 18. The wearable heads-up display of claim16 wherein the intensity of at least one of the side lobes of thehologram is greater than the intensity of the primary hologram peak. 19.The wearable heads-up display of claim 16 wherein the initial set offringes and each additional set of fringes meta-interfere mostconstructively at a depth through the hologram between the first surfaceand the second surface; the initial set of fringes and each additionalset of fringes meta-interfere at least partially destructively at thefirst surface; the initial set of fringes and each additional set offringes meta-interfere at least partially destructively at the secondsurface; the magnitude of Δn at the first surface is equal to or lessthan 50% of the greatest magnitude of Δn within the hologram; and themagnitude of Δn at the second surface is equal to or less than 50% ofthe greatest magnitude of Δn within the hologram.
 20. The wearableheads-up display of claim 16 wherein the initial set of fringes and eachadditional set of fringes meta-interfere most destructively at a depththrough the hologram between the first surface and the second surface;the initial set of fringes and each additional set of fringesmeta-interfere at least partially constructively at the first surface;the initial set of fringes and each additional set of fringesmeta-interfere at least partially constructively at the second surface;at least one of: the first surface and the second surface possess thegreatest magnitude of Δn; the minimum magnitude of Δn within the volumeof the hologram is no greater than 50% of the greatest magnitude of Δnwithin the hologram; and the magnitude of Δn decreases continuously fromthe first surface to the minimum value of Δn within the hologram and themagnitude of Δn decreases continuously from the second surface to theminimum value of Δn within the hologram.
 21. The wearable heads-updisplay of claim 16 wherein the hologram comprises awavelength-multiplexed hologram, the wavelength-multiplexed hologramcomprising a blue hologram, a green hologram, a red hologram, and aninfrared hologram.